Newcastle United vs Liverpool: passing network analysis

Liverpool defeated Newcastle 6-0 at St James’ Park. Below is the passing network analysis for Liverpool split between the first 75 minutes of the match and the rest of the match up to full time. I focussed just on Liverpool here. More information on how these are put together is available here in my previous posts on this subject.

The reason I separated the networks into these two periods was that I noticed how Liverpool’s passing rate changed massively after Steven Gerrard was substituted and the fifth goal was scored. During the first 75 minutes, Liverpool attempted 323 passes with a success rate of 74% and a 45% share of possession. After this, Liverpool attempted 163 passes with an accuracy of 96% and a 60% share of possession. Liverpool attempted 34% of their passes in this closing period. Let’s see how this looks in terms of their passing network.

The positions of the players are loosely based on the formations played, although some creative license is employed for clarity. It is important to note that these are fixed positions, which will not always be representative of where a player passed/received the ball. The starting eleven is shown on the pitch for the first 75 minutes, with Borini replacing Gerrard in the second network.

Passing networks for Liverpool for the first and second halfs against Swansea City from the match at Anfield on the 17th February 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. Players with an * next to their name were substituted. Click on the image for a larger view.

Passing networks for Liverpool for the first 75 minutes and up to full time against Newcastle United from the match at St James’ Park on the 27th April 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. Click on the image for a larger view.

Liverpool’s passing was quite balanced for the first 75 minutes of the match, with a varied passing distribution. There was a stronger bias towards the right flank compared with the left flank as Gerrard drifted right to combine with Johnson and Downing. The passing influence scores were also evenly distributed across the whole team with Gerrard and Lucas being the top two. A contrast with some previous matches is the lack of strong links along the back line, which indicates less reliance on recycling of possession in deeper areas. Instead, Liverpool were seeking to move the ball forward more quickly and played the ball through the whole team.

He makes us happy

After Gerrard and Lucas, the next most influential player was Coutinho, who put in a wonderfully creative performance as the attacking fulcrum of the team. He linked well with all of Liverpool’s forward players and threaded several dangerous passes to his team-mates including an assist and a ‘second goal assist’ (defined as a pass to the goal assist creator) for the second goal according to EPL-Index. His creative exploits thus far have been hugely promising during his first 10 appearances.

Sterile domination

The final period of the match saw Liverpool really rack up the passing numbers as mentioned earlier. Clearly, this is easier to do when 5 or 6 goals clear but it is still potentially illustrative to see how this was accomplished. The main orchestrator’s of this were Lucas and Henderson who were 28/28 and 35/35 for passes attempted/completed during this period. Henderson was 21/24 from the first 75 minutes, so this was quite a rapid increase with his shift in role after Gerrard went off and the state of the game.

Your challenge should you wish to accept it

Admittedly Newcastle were very poor in this match but Liverpool took advantage to enact a severe thrashing. This was accomplished without Suárez, which leads to obvious (premature?) questions about whether his absence improved Liverpool’s overall balance and play. Assuming that Suárez doesn’t leave in the summer, one of Bredan Rodgers’ key tasks will be developing a system that gets the best out of the attacking talents of Suárez, Coutinho and Sturridge. It could be quite tasty if he manages to accomplish this.

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Liverpool vs Zenit St Petersburg: passing network analysis

Liverpool beat Zenit 3-1 at Anfield but went out of the Europa League on away goals. Below is the passing network analysis for Liverpool for both the first hour and the final 30 minutes of the match. This coincides with Liverpool’s sumptuous third goal and the double substitution that saw Assaidi and Shelvey replace Henderson and Allen. More information on how these passing networks are put together is available here in my previous posts on this subject.

The positions of the players are loosely based on the formations played by the two teams, although some creative license is employed for clarity. It is important to note that these are fixed positions, which will not always be representative of where a player passed/received the ball. The starting eleven is shown on the pitch for the first hour, with the substitutes shown for the final 30 minutes. Sterling was only on the pitch for a brief period so I’ve omitted him from the second network.

Passing networks for Liverpool for the first and second halfs against Swansea City from the match at Anfield on the 17th February 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. Players with an * next to their name were substituted. Click on the image for a larger view.

Passing networks for Liverpool for the first 60 minutes and final 30 minutes of the match against Zenit St Petersburg from the match at Anfield on the 21st February 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. Players with an * next to their name were substituted. Click on the image for a larger view.

Liverpool’s initial selection circulated possession well within the midfield zone, which is perhaps unsurprising given how possession friendly the midfield was. Compared with Coutinho and Suárez in the match against Swansea, Henderson and Allen primarily look to maintain possession rather than being more direct with their approach play. This meant that Liverpool dominated possession and kept Zenit pinned back in their half generally. Enrique and Johnson were also heavily involved and provided a great deal of width. At the hub of Liverpool’s play was Lucas who knitted things together superbly and combined effectively with all of his team mates.

Zenit did generally defend very well though and Liverpool struggled to create particularly incisive moves, although Allen’s goal was the result of excellent interplay between Henderson and Enrique (the strongest passing link in the first hour). Two set-piece goals from Suárez though set the platform for a potentially memorable comeback after Zenit’s away goal.

Anything could happen in the next half hour

Liverpool’s double substitution after the third goal saw two more direct attacking threats joining the fray as the side looked for a potential tie-winning goal. However, looking at the passing network for the last half hour, Liverpool struggled to bring their attacking players into the game. Liverpool shot frequency actually declined in this period with a succession of crosses from both open-play and set-pieces being delivered into the box. Zenit defended particularly well during this period and maintained possession for short periods to stem the tide of Liverpool attacks. They also pressed high up the pitch which saw some nervous moments in the crowd as well as the odd passage on the pitch! While the changes likely didn’t help Liverpool to any great extent, chances were still created that could have won the tie plus Zenit also boxed clever while often under a lot of pressure.

Over and out

Unfortunately Liverpool weren’t able to score that crucial fourth goal in the final 30 minutes that could have seen them go through. On a personal note, it was a privilege to be a part of a fantastic atmosphere at Anfield, which nearly saw an improbable comeback to add to Liverpool Football Club’s folklore.

Liverpool vs West Bromwich Albion: passing network analysis

Liverpool lost to West Bromwich Albion 2-0 at Anfield. Below is the passing network analysis for Liverpool and West Brom. More information on how these are put together is available here in my previous posts on this subject.

The positions of the players are loosely based on the formations played by the two teams, although some creative license is employed for clarity. It is important to note that these are fixed positions, which will not always be representative of where a player passed/received the ball. Only the starting eleven is shown on the pitch, as the substitutes weren’t hugely interesting from a passing perspective in this instance.

Passing network for Manchester City and Liverpool from the match at the Etihad on the 3rd February 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. The size and colour of the markers is relative to the players on their own team i.e. they are on different scales for each team. Only the starting eleven is shown. Players with an * next to their name were substituted. Click on the image for a larger view.

Passing network for Liverpool and West Brom from the match at Anfield on the 11th February 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. The size and colour of the markers is relative to the players on their own team i.e. they are on different scales for each team. The player markers are coloured by the number of times they lost possession during the match, with darker colours indicating more losses. Only the starting eleven is shown. Players with an * next to their name were substituted. Click on the image for a larger view.

There are some contrasting features between the two sides here. Liverpool’s standard recycling of possession in deeper areas is evident, with interplay between Reina, the back four and the midfield two of Lucas and Gerrard. West Brom showed some similar features, although the link between their centre backs is much weaker than the link between Agger and Carragher.

Mulumbu and Morrison were impressive for West Brom, linking well with the players around them. They formed some nice triangular passing structures with those around them, particularly with their midfield partner Yacob. Based on their passing network, West Brom passed the ball around well when they had it although Long wasn’t hugely involved (he did provide his usual nuisance value though).

One of the major differences is how both sides involved their respective centre forwards. Long generally either received the ball from deeper areas e.g. the long link between himself and Foster (although many of the passes were unsuccessful) or by linking up with Morrison, who was typically the most advanced of West Brom’s central midfielders. In contrast, the link between Shelvey and Suárez is almost non-existent. Given that these two were ostensibly Liverpool’s two most attacking players, the lack of interplay between them was disappointing.

Ineffectual width

With Henderson and Downing continuing on their “unnatural” sides, Liverpool’s fullbacks had plenty of space to move into down the flanks. This meant they were often a natural passing outlet for their team mates and this is highlighted by the high passing influence scores they both received. Unfortunately, much of the attacking impetus that Enrique and Johnson provided was highly wasteful. As noted on the Oh you beauty blog, their pass completion in the final third was woeful. Between them, Enrique and Johnson accounted for 30% of Liverpool’s total losses of possession. Enrique misplaced 9 passes within his own half also, as noted by WhoScored. Generally I’ve interpreted a higher passing influence score as being a good thing but perhaps in this instance this wasn’t the case.

That is why we like him

Aside from Enrique and Johnson, the main passing influence for Liverpool was Lucas. Lucas’ absolute and relative passing influence within in the team has been steadily increasing over recent matches, which is encouraging as he recovers from his injury issues. Unfortunately for Liverpool, Gerrard, Henderson and Downing had less influence than in recent weeks, which alongside the lack of partnership between Shelvey and Suárez, went some way to Liverpool struggling to open up West Brom.

Manchester City vs Liverpool: passing network analysis

Manchester City drew 2-2 with Liverpool at the Etihad. Below is the passing network analysis for Manchester City and Liverpool. More information on how these are put together is available here in my previous posts on this subject.

The positions of the players are loosely based on the formations played by the two teams, although some creative license is employed for clarity. It is important to note that these are fixed positions, which will not always be representative of where a player passed/received the ball. Only the starting eleven is shown on the pitch, as the substitutes weren’t hugely interesting from a passing perspective in this instance.

Passing network for Manchester City and Liverpool from the match at the Etihad on the 3rd February 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. The size and colour of the markers is relative to the players on their own team i.e. they are on different scales for each team. Only the starting eleven is shown. Players with an * next to their name were substituted. Click on the image for a larger view.

Passing network for Manchester City and Liverpool from the match at the Etihad on the 3rd February 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. The size and colour of the markers is relative to the players on their own team i.e. they are on different scales for each team. Only the starting eleven is shown. Players with an * next to their name were substituted. Click on the image for a larger view.

In the reverse fixture, Yaya Touré and De Jong were very influential for City but Touré was away at the African Cup of Nations, while De Jong joined Milan shortly after that fixture. Their replacements in this game, Barry and Garcia, were less influential, although Barry had the strongest passing influence for City in this match, with Milner second. The central midfield two, Lucas and Gerrard, were very influential for Liverpool and strongly dictated the passing patterns of the team. They both linked well with the fullbacks and wider players, while Lucas also had strong links with Suárez and Sturridge. Certainly in this area of the pitch, Liverpool had the upper hand over City and this provided a solid base for Liverpool in the match.

No Silva lining

Something that Liverpool did particularly well was limit the involvement of David Silva, who posted his worst pass completion rate (73% via EPL-Index) this season. Usually, Silva completes a pass every 96 seconds this season, whereas against Liverpool it was every 162 seconds. While Mancini’s tactical change did bring Silva more into the game briefly, overall it had a negligible impact upon Silva’s influence when comparing the networks before and after the substitution. However, one of the few occasions where Silva was able to find some time and space, he combined well with James Milner to help create City’s first goal. Goes to show it is difficult to keep good players quiet for a whole match.

Moving forward

Similarly to the Arsenal game, Liverpool showed less of an emphasis upon recycling the ball in deeper areas. Instead, they favoured moving the ball forward more directly, with Enrique often being an outlet for this via Reina and Agger. Liverpool’s fullbacks combined well with their respective wide-players, while also being strong options for Lucas and Gerrard. Strurridge was generally excellent in this match and was more influential in terms of passing than in his previous games against Norwich and Arsenal, combining well with Suárez, Lucas and Gerrard.

At least based on the past few games, Liverpool have shown the ability to alter their passing approach with a heavily possession orientated game against Norwich, followed up by more direct counter-attacking performances against Arsenal and Manchester City. The game against City was particularly impressive as this was mixed in with some good control in midfield via Lucas and Gerrard, which was absent against Arsenal. How this progresses during Liverpool’s next run of fixtures will be something to look out for.

Arsenal vs Liverpool: passing network analysis

Arsenal and Liverpool drew 2-2 at the Emirates, as Arsenal came back from two goals down. Below is the passing network analysis for Arsenal and Liverpool. More information on how these are put together is available here in my previous posts on this subject.

The positions of the players are loosely based on the formations played by the two teams, although some creative license is employed for clarity. It is important to note that these are fixed positions, which will not always be representative of where a player passed/received the ball. The starting eleven is shown on the pitch, while Enrique and Santos, who came on as substitutes are shown on the sidelines.

Passing network for Liverpool and Norwich City from the match at Anfield on the 19th January 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. Only the starting eleven is shown.

Passing network for Arsenal and Liverpool from the match at the Emirates on the 30th January 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. The size and colour of the markers is relative to the players on their own team i.e. they are on different scales for each side. The starting eleven is shown on the pitch, with the substitutes on the sidelines. Click on the image for a larger view.

The contrast between the two teams approach is apparent, with Arsenal dominating possession (62% according to EPL-Index), which is reflected in their much stronger passing links across the team. Much of Arsenal’s play went through Aaron Ramsey, who played a similar role to that played by Mikel Arteta in the reverse fixture, although Arsenal saw more of the ball in this match. Arsenal’s midfield-three of Ramsey, Wilshire and Cazorla combined very well and dictated the passing patterns of the side excellently.

For Liverpool, the story was slightly different. The side was happy to counter-attack, which meant that the usual recycling of possession in deeper areas was less prevalent than for example against Norwich. Most of Liverpool’s play went through Henderson and Gerrard (again Liverpool’s major passing influence), with Johnson and Downing providing good support down the left and right flanks respectively. Daniel Agger was also able to influence the game from deeper positions, with his passing influence score being third behind Gerrard and Downing. Suárez was reasonably involved, combining well with Agger, Johnson and Henderson.

Hymns & Arias

In terms of passing influence, Ramsey was the undoubted star of the show. He conducted Arsenal’s play from deep beautifully, completing over 100 passes in the process. Obviously this was partially a result of Liverpool’s approach, which allowed him the time and space to dictate play but he combined well with Arsenal’s attacking players throughout the match. Gerrard was the major influence for Liverpool, while Jordan Henderson provided a passing option higher up the pitch and brought Downing, Suárez and to a lesser extent, Sturridge into the game. This was an important function in the team’s counter-attacking.

Liverpool delivered a different passing performance in this match. There are many parallels with the Everton match here, where Liverpool had a similar passing network and employed a more pragmatic counter-attacking style. It will be interesting to see if they use such tactics in the next match against Manchester City

Liverpool vs Norwich City: passing network analysis

Liverpool beat Norwich City 5-0 at Anfield while posting some impressive passing statistics. I’ve previously used network analysis to assess Liverpool’s passing this season. It has been a while since I last posted something on this but now seemed a good time to get back to it.

Below is the passing network for both Liverpool and Norwich City. The positions of the players are loosely based on the formations played by the two teams, although some creative license is employed for clarity e.g. Suárez’s position is shifted left-of-centre. It is important to note that these are fixed positions, which will not always be representative of where a player passed/received the ball. Only the starting eleven are shown in this instance.

Passing network for Liverpool and Norwich City from the match at Anfield on the 19th January 2013. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The player markers are sized according to their passing influence, the larger the marker, the greater their influence. Only the starting eleven is shown.
Liverpool: Jones (1), Johnson (2), Agger (5), Carragher (23), Wisdom (47), Lucas* (21), Gerrard (8), Henderson* (14), Suárez (7), Sturridge* (15), Downing (19)
Norwich: Bunn (28), Garrido (18), R Bennett (24), Turner (6), Martin (2), Johnson (4), Tettey (27), E Bennett* (17), Howson (8), Snodgrass* (7), Holt (9)

There is a stark contrast between how the two teams approached passing the ball. Looking at Jones, the back four and Lucas, there are a multitude of connections between them as Liverpool aim to build from the back. Furthermore, Henderson and Gerrard are heavily involved in this area as the team aims to recycle possession – look at the strong links between them, Lucas and the centre-backs. This is completely missing in Norwich’s network as they sought to be more direct – see the long link between Bunn and Holt for example. Norwich created relatively little during the game and it is clear from their passing network that Holt was fairly uninvolved. I’ll not delve into Norwich’s passing network any further.

Sharing the load

An important diagnostic for network analysis is a measure known as “closeness centrality”, which in this context is dictated by the number of passes played and received by a given player. The higher the value the better and this can be thought of as the “passing influence” that a player has on their team. The absolute values aren’t important in this instance* so the main thing to look at is the relative size of the circles for each team. One of the major aspects of Liverpool’s network is that all of the outfield players aside from Sturridge were heavily involved in the passing movements of the team. Sturridge’s lesser involvement isn’t a criticism as such, as he clearly combined well with Liverpool’s more advanced players. In some ways, strikers can be disadvantaged by such a measure as they have less opportunity to get involved with everyone in the team, which can also be the case for goalkeepers. A more even distribution of passing responsibilities allows a side to create multiple attacking angles/opportunities – notice the large level of criss-crossing of the networks for Liverpool’s attacking players. Liverpool’s front-five plus Glen Johnson had a large amount of interplay with able support from Wisdom and Lucas.

O Captain! My Captain!

However, there was clearly a stand-out performer in terms of passing influence as Steven Gerrard dominates the passing network for Liverpool. Gerrard was the hub of the team’s passing. This combined with the rest of the team stepping up to the (passing?) plate, meant that Liverpool delivered an excellent passing performance. Whether they can continue this level of performance over the coming games will be crucial.

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*At some point I want to put these measures into a more quantitative context, which will hopefully add further detail regarding how Liverpool’s passing develops. 

Luis Suárez: Stuck in the middle?

Luis Suárez, the latest member of Liverpool’s one-man team, has been playing rather well this season. At the time of writing, he is 2nd in the top scorers list with 15 goals, while also boasting the most chances created from open play in the league. Even more impressively he manages to accomplish this while nefariously drowning kittens in his spare time*.

This increased rate of scoring compared with last season has been much needed due to Liverpool’s lack of attacking options. The question is, what has changed?

Just can’t score enough?

Firstly, Suárez is averaging a goal every 8.4 shots this season compared to 11.6 last season. Secondly, he is shooting more often this season as he shoots every 15 minutes on average compared with a shot every 20 minutes last season. The combination of these two features would naturally lead to an enhanced scoring rate. So far, so good but can we delve a little deeper into Suárez’s shooting data?

Below is a summary of Suárez’s shooting across the last two seasons in the league based on data collected from Opta’s chalkboard services. The data is aggregated positionally to examine how regularly Suárez shoots from a particular location and also how efficient his goalscoring is from these areas. This provides us with indicators of the quality of a shot i.e. the distance from the goal-line coupled with the angle from which the shot is taken. Other factors will impact the quality of the shooting opportunity such as the position of the goalkeeper, whether the shot is attempted with the foot or the head and the number of players between the shooter and the goal. This last point is probably especially important for someone like Suárez who tends to see a lot of his shots blocked.

Comparison between Luis Suárez’s shooting and goalscoring from the 2011/12 and 2012/13 seasons. The circles designate areas from which Suárez took a shot from and are sized by the number of shots taken from that area. The areas correspond to horizontal bands from 0-10, 10-20 and more than 20 yards from the goal-line. The grey dotted lines show where the 10 and 20 yard lines are situated. The vertical bands are ordered along the lines of the touchline, edge of the 18 yard box and the 6 yard box. The numbers within each marker correspond to the average number of shots attempted per goal scored in that area. Markers without a number mean that no goals were scored from that area.

The first thing to note about the goals Suárez scores is that across both seasons, the vast majority of his goals come from relatively central areas within the penalty area or just on the edge of it. Furthermore, we can see that Suárez appears to shoot a lot from locations where he doesn’t generally score from. His overall number of shots is similar across the two seasons, although there are still 16 matches still to play this season. There has been some change in the areas from which he has been shooting this season, with close to twice as many shots being taken from the central zone that is more than 20 yards from the goal-line. This has been compensated with fewer attempts from the less than 10 yard zone.

The main difference between the two seasons is that he is now scoring goals more within the 10-20 yards central area and at a reasonable rate. Suárez is now far more efficient in this zone in terms of goalscoring, with 1 goal from 34 shots last season compared with 5 goals from 29 shots this season. It is the goals scored from within this zone that have led to his increased goalscoring rate.

Slipping and sliding

So we can see that compared with himself, Suárez has improved this season. The question is how does he compare with his peers? I don’t have a large enough dataset to do a like-for-like comparison but we can contrast his numbers with data collected by the Different Game blog. The zones are slightly different here but for the central zone within the penalty area, Suárez averaged 7.5 shots per goal last season and 4.5 this season. So compared to the 6 shots per goal average over last season and this, he is better than his peers this season but underperformed last season. There are caveats here in that my figures include penalties, although after his penalty “attempts” last season, Suárez hasn’t been taking penalties this season (not that Liverpool have had many to take and he only took one penalty in the league last season). Furthermore, this is for all players taking shots and potentially you might prefer to compare to other strikers.

In general, we can see that Suárez has been more efficient this season in terms of his goalscoring and that his conversion compares favourably with his peers. The reasons for this are less clear and could be due to a multitude of factors including luck, his role within the team this season, Liverpool’s overall tactics and even less tangible factors such as “off-field distractions”. One thing that is clear from this analysis is that if you want Luis Suárez to score goals, he needs to be taking his shots from central areas. Brendan Rodgers has hinted at playing him as a wide-forward now that Daniel Sturridge has arrived; preserving Suárez’s current goalscoring record would be a challenge if he ends up taking more shots from more difficult angles, which may occur due to his natural position being out-wide. Over the last season and a half, Suárez has taken 103 shots from the wide positions for a return of 5 goals.

Based on this analysis and watching him play a lot, I would say that in certain circumstances, Suárez is a good finisher but that he is wasteful in terms of his decision making. Since the beginning of 2011/12, just over 40% of his shots were taken from areas out-wide where he rarely scores from, coupled with 36% of all of his shots being blocked (although this has improved this season). While the “scorer of great goals, rather than a great goal scorer” line has been an attractive label for Suárez during his Liverpool career, the analysis presented here indicates that he is more nuanced than that. Mind you, “a reasonably efficient goalscorer provided that he is in a central shooting position within approximately 20 yards of goal who is capable of scoring the odd goal that takes your breath away” is a bit more of a mouthful.

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Data sources: EPL-Index, Squawka and StatsZone.

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*This is not true.

Assessing team playing styles

The perceived playing style of a football team is a much debated topic with conversations often revolving around whether a particular style is “good/bad” or “entertaining/boring”. Such perceptions are usually based upon subjective criteria and personal opinions. The question is whether the playing style of a team can be assessed using data to categorise and compare different teams.

WhoScored report several variables (e.g. data on passing, shooting, tackling) for the teams in the top league in England, Spain, Italy, Germany and France. I’ve collated these variables for last season (2011/12) in order to examine whether they can be used to assess the playing style of these sides. In total there are 15 variables, which are somewhat limited in scope but should serve as a starting point for such an analysis. Goals scored or conceded are not included as the interest here is how teams actually play, rather than how it necessarily translates into goals. The first step is to combine the data in some form in order to simplify their interpretation.

Principal Component Analysis

One method for exploring datasets with multiple variables is Principal Component Analysis (PCA), which is a mathematical technique that attempts to find the most common patterns within a dataset. Such patterns are known as ‘principal components’, which describe a certain amount of the variability in the overall dataset. These principal components are numbered according to the amount of variance in the dataset that they account for. Generally this means that only the first few principal components are examined as they account for the greatest percentage variance in the dataset. Furthermore, the object is to simplify the dataset so examining a large number of principal components would somewhat negate the point of the analysis.

The video below gives a good explanation of how PCA might be applied to an everyday object.

Below is a graph showing the first and second principal components plotted against each other. Each data point represents a single team from each of the top leagues in England, Spain, Italy, Germany and Italy. The question though is what do each of these principal components represent and what can they tell us about the football teams included in the analysis?

Principal component analysis of all teams in the top division in England, Spain, Italy, Germany and France. Input variables are taken from WhoScored.com for the 2011/12 season.

The first principal component accounts for 37% of the variance in the dataset, which means that just over a third of the spread in the data is described by this component. This component is represented predominantly by data relating to shooting and passing, which can be seen in the graph below. Passing accuracy and the average number of short passes attempted per game are both strongly negatively-correlated (r=-0.93 for both) with this principal component, which suggests that teams positioned closer to the bottom of the graph retain possession more and attempt more short passes; unsurprisingly Barcelona are at the extreme end here. Total shots per game and total shots on target per game are also strongly negatively-correlated (r=-0.88 for both) with the first principal component. Attempted through-balls per game are also negatively correlated (r=-0.62). In contrast, total shots conceded per game and total aerial duels won per game are positively-correlated (r=0.65 & 0.59 respectively). So in summary, teams towards the top of the graph typically concede more shots and win more aerial duels, while as you move down the graph, teams attempt more short passes with greater accuracy and have more attempts at goal.

The first principal component is reminiscent of a relationship that I’ve written about previously, where the ratio of shots attempted:conceded was well correlated with the number of short passes per game. This could be interpreted as a measure of how “proactive” a team is with the ball in terms of passing and how this transfers to a large number of shots on goal, while also conceding fewer shots. Such teams tend to have a greater passing accuracy also. These teams tend to control the game in terms of possession and shots.

The second principal component accounts for a further 18% of the variance in the dataset [by convention the principal components are numbered according to the amount of variance described]. This component is positively correlated with tackles (0.77), interceptions (0.52), fouls won (0.68), fouls conceded (0.74), attempted dribbles (0.59) and offsides won (0.63). In essence, teams further to the right of the graph attempt more tackles, interceptions and dribbles which unsurprisingly leads to more fouls taking place during their matches.

The second principal component appears to relate to changes in possession or possession duels, although the data only relates to attempted tackles, so there isn’t any information on how successful these are and whether possession is retained. Without more detail, it’s difficult to sum up what this component represents but we can describe the characteristics of teams and leagues in relation to this component.

Correlation score graph for the principal component analysis. PS stands for Pass Success.

The first and second components together account for 55% of the variance in the dataset. Adding more and more components to the solution would drive this figure upwards but in ever diminishing amounts e.g. the third component accounts for 8% and the fourth accounts for 7%. For simplicity and due to the further components adding little further interpretative value, the analysis is limited to just the first two components.

Assessing team playing styles

So what do these principal components mean and how can we use them to interpret team styles of play? Putting all of the above together, we can see that there are significant differences between teams within single leagues and when comparing all five as a whole.

Within the English league, there is a distinct separation between more proactive sides (Liverpool, Spurs, Chelsea, Manchester United, Arsenal and Manchester City) and the rest of the league. Swansea are somewhat atypical, falling between the more reactive English teams and the proactive 6 mentioned previously. Stoke could be classed as the most “reactive” side in the league based on this measure.

There isn’t a particularly large range in the second principal component for the English sides, probably due the multiple correlations embedded within this component. One interesting aspect is how all of the English teams are clustered to the left of the second principal component, which suggests that English teams attempt fewer tackles, make fewer interceptions and win/concede fewer fouls compared with the rest of Europe. Inspection of the raw data supports this. This contrasts with the clichéd blood and thunder approach associated with football in England, whereby crunching tackles fly in and new foreign players struggle to adapt to the intense tackling approach. No doubt there is more subtlety inherent in this area and the current analysis doesn’t include anything about the types of tackles/interceptions/fouls, where on the pitch they occur or who perpetrates them but this is an interesting feature pointed out by the analysis worthy of further exploration in the future.

The substantial gulf in quality between the top two sides in La Liga from the rest is well documented but this analysis shows how much they differed in style with the rest of the league last season. Real Madrid and Barcelona have more of the ball, take more shots and concede far fewer shots compared with their Spanish peers. However, in terms of style, La Liga is split into three groups: Barcelona, Real Madrid and the rest. PCA is very good at evaluating differences in a dataset and with this in mind we could describe Barcelona as the most “different” football team in these five leagues. Based on the first principal component, Barcelona are the most proactive team in terms of possession and this translates to their ratio of shots attempted:conceded; no team conceded fewer shots than Barcelona last season. This is combined with their pressing style without the ball, as they attempt more tackles and interceptions relative to many of their peers across Europe.

Teams from the Bundesliga are predominantly grouped to the right-hand-side of the second principal component, which suggests that teams in Germany are keen to regain possession relative to the other leagues analysed. The Spanish, Italian and French tend to fall between the two extremes of the German and English teams in terms of this component.

All models are wrong, but some are useful

The interpretation of the dataset is the major challenge here; Principal Component Analysis is purely a mathematical construct that doesn’t know anything about football! While the initial results presented here show potential, the analysis could be significantly improved with more granular data. For example, the second principal component could be improved by including information on where the tackles and interceptions are being attempted. Do teams in England sit back more compared with German teams? Does this explain the lower number of tackles/interceptions in England relative to other leagues? Furthermore, the passing and shooting variables could be improved with more context; where are the passes and shots being attempted?

The results are encouraging here in a broad sense – Barcelona do play a different style compared with Stoke and they are not at all like Swansea! There are many interesting features within the analysis, which are worthy of further investigation. This analysis has concentrated on the contrasts between different teams, rather than whether one style is more successful or “better” than another (the subject of a future post?). With that in mind, I’ll finish with this quote from Andrés Iniesta from his interview with Sid Lowe for the Guardian from the weekend.

…the football that Spain and Barcelona play is not the only kind of football there is. Counter-attacking football, for example, has just as much merit. The way Barcelona play and the way Spain play isn’t the only way. Different styles make this such a wonderful sport.

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Background reading on Principal Component Analysis

  1. RealClimate

West Bromwich Albion vs Liverpool: passing network analysis

Liverpool began their season with a disappointing result against West Bromwich Albion at the Hawthorns. Much has been made since Brendan Rodgers’ appointment about his passing philosophy, so the focus here will be upon analysing how Liverpool passed the ball against West Brom.

Passing network analysis

One method of analysing passing by a football team is network analysis, which I’ve used previously to assess Liverpool’s passing against FC Gomel. The idea with network analysis is that the connections between players are analysed to look at passing patterns in the team and to identify key players in the network in terms of passing. The number of passes played and received by each player is collated according to the player they passed to and who they received from respectively. The data for passes played and received is taken from the Stats Zone application, which was kindly provided by the excellent Anfield-Index. One caveat to note is that throw-ins are included, which boosts Johnson and Kelly’s passes completed in particular.

Below is the passing network for Liverpool and shows completed passes only. The larger and darker the arrow is, the greater the number of passes played by one player to another. The positions of the players are based on their average positions during the match provided by WhoScored, although Lucas and Allen are slightly separated horizontally for clarity as their average positions were practically next to each other. It is important to note that these are the average positions, which will not always be representative of where a player passed/received the ball. Also, only the starting 11 is shown as the substitutes had a fairly limited impact upon the game in terms of passing.

Passing network for Liverpool from the away match against West Bromwich Albion on the 18th August 2012. Only completed passes are shown. Darker and thicker arrows indicate more passes between each player. The position of each marker is based upon their average position and the size of each marker is related to their closeness centrality, which is described in the text below. Asterisk indicates players who did not play the full match. Only the starting eleven is shown.

The main features in the above network are the reciprocal passes played between the defenders and the criss-crossing of passes in the midfield zone. Liverpool clearly kept the ball efficiently in deeper areas as the back four plus Lucas and Allen retained the ball well. The main issue for Liverpool was getting the ball to their attackers further up the pitch. Borini and Downing received the ball just 31 and 33 times respectively, with Downing in particular tending to pass the ball back to players in deeper areas; Downing completed a pass to Suárez twice and Borini once. Borini tended to combine with Johnson and Suárez in the main, passing to both of them on 7 occasions. Liverpool did effectively get the ball to Suárez, as he received the ball on 51 occasions and he was Liverpool’s main attacking outlet. Suárez tended to receive the ball from players in wide areas and from Lucas and Allen, whereas against Gomel the main link was with Gerrard and the quick interchanging of passes between them was less in evidence sadly.

Where you gonna pass to now, where you gonna go?

One of the useful tools of network analysis is that you can derive measures that indicate which players in the team are the most influential in terms of passing. One of these measures is known as “closeness centrality”, which in this context is dictated by the number of passes played and received by a given player. The key aspect of this measure is that it is greater when the passes that the player plays and receives are distributed more evenly across the team. If a hypothetical player makes 100 passes in a match and receives the ball 100 times, they would have a greater closeness centrality if they passed and received the ball 10 times to and from each team-mate compared to if they simply passed the ball back and forth to just 1 team-mate. Players with a larger closeness centrality score are interpreted as being a greater influence upon the passing of the team as they dictate the movement of the ball within the side.

In the figure above, the size of the player markers is dictated by their closeness centrality score. Joe Allen was Liverpool’s stand out player as he dictated Liverpool’s passing play. He generally received the ball from his centre-backs and Johnson prior to playing his passes. He linked well with Johnson and Borini on the left, his midfield partner Lucas and Suárez further forward. A feature of Allen’s play was his movement to make himself available for a pass and he received a pass on 62 occasions, more than any other player.

Skrtel had the next highest closeness score, although he was some way behind Allen. Agger was far less effective compared to the Gomel match, partly due to the sending off but also due to his passing recipients being lesser in scope as he favoured passes to Johnson, Skrtel and Allen. Lucas was also less of an influence, again partly due to not playing the full game but also due to being less central to the teams passing. Johnson was more effective than Kelly from full-back and was probably Liverpool’s most influential attacking force as he played high up the pitch on the left and created 3 scoring opportunities according to the EPL-Index Stats Centre. Downing and Borini’s involvement was very limited compared to their team-mates (only Reina was less involved). The involvement of Suárez and Gerrard was also disappointing. Overall, the lack of involvement of Liverpool’s front-4 was a hindrance over the course of the match, as most of the play was contained in the defensive and midfield zones.

Hey Joe

Liverpool’s passing against West Brom was reasonable, particularly in the 1st half and there were definite signs of Brendan Rodgers’ philosophy bedding in. However, the lack of involvement of the front-4 and in particular, Borini and Downing was disappointing. The major bright spot was the performance of Joe Allen, who dictated the passing play of the team to good effect. Unfortunately, Lucas wasn’t up to his usual level, which may be due to his ongoing recovery from injury and also this match being the first time he started with Allen. Hopefully future games will see this partnership blossoming as they begin to complement each other in terms of their roles within the team. Such a partnership could be crucial in implementing the control that Brendan Rodgers desires.

Liverpool 2012/13: statistical predictions

With the new Premier League season starting tomorrow, I thought I would jot down some predictions about how Liverpool will do statistically next season. These are meant as a bit of fun and are basically a collection of some random thoughts that I’ve had. I look forward to revisiting these later in the season with embarrassment.

Liverpool to average more than 500 short passes per game

I’ve previously investigated the number of short passes that teams made per game last season, which showed that Swansea attempted 497 per game, while Liverpool attempted 440. Given Brendan Rodgers’ possession orientated style of play and Liverpool’s gradual adaptation to it in pre-season, I would expect them to increase that number. It will be interesting to see how much resting with the ball that Liverpool actually do.

Lucas to attempt and complete more passes per game than any other player in the league

Provided that he fully recovers from his injury, I expect Lucas to be a crucial element in Rodgers’ passing philosophy this season. Indeed, against Gomel, Lucas and Agger were the fulcrum of the team’s passing. With that in mind, I think Lucas will see a lot of the ball and will dictate Liverpool’s passing play this season. Whether he’ll actually top the attempted and completed passes count is possibly going too far but I wouldn’t be surprised to see him up there with the likes Mikel Arteta and Yaya Touré.

Liverpool to cross less than the league average

Liverpool appeared to focus much of their play last season on crossing with scant reward. Swansea on the other hand, crossed far less. Rodgers may well regard crossing as an inefficient means of attacking, due to the high likelihood of conceding possession due to the overall low accuracy of crossing. With this in mind and the signings for the wide forward positions that Liverpool have made, I would expect Liverpool to cross far less and that their ratio of attacking half passes to attempted open play crosses to increase above the league average.

Luis Suárez to be involved in a higher percentage of Liverpool’s goals

Despite missing a large number of matches through suspension last season, Suárez still managed to either score or assist 30% of Liverpool’s 47 league goals. This was mainly a consequence of Liverpool’s poor shot conversion record, which Suárez himself no doubt contributed towards. He created more chances than any other Liverpool player (64) but only 3 actually resulted in a goal. I hope/pray that Liverpool’s shot conversion improves this season and I would expect Suárez to once again be Liverpool’s main creator and possibly their top scorer as well. Thus I think that Suárez will either score or create more than 30% of Liverpool’s goals next season.

Liverpool to create better quality chances next season

In 2011/12, Liverpool created 485 chances with 19% being classed as “clear cut” by Opta. I expect Liverpool under Rodgers to be more patient in the final third, which could result in them creating more “clear cut” chances and hopefully scoring more of them! In short, I expect Liverpool to create more clear chances and for their proportion relative to all chances to increase.

How many points will Liverpool get this season?

This is less of a prediction, more a complete shot in the dark but I think Liverpool will get 65 points this season. That is unlikely to be enough for fourth place but a 13 point increase on last season would be a sign of good progress. Maybe, just maybe, the team might quickly adapt to Rodgers’ philosophy and combine that with a little luck and push into the 70-75 point range, which would likely mean a top 4 place. Some would probably refer to that as utopia.

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Statistics are sourced from WhoScored and EPL-Index. I’ll revisit these predictions around the half way point of the season and at the end of the season.