Luis Suárez: Home & away

Everyone’s favourite riddle wrapped in an enigma was a topic of Twitter conversation between various analysts yesterday. The matter at hand was Luis Suárez’s improved goal conversion this season compared to his previous endeavours. Suárez has previously been labelled as inefficient by members of the analytics community (not the worst thing he has been called mind), so explaining his upturn is an important puzzle.

In the 2012/13 season, Suárez scored 23 goals from 187 shots, giving him a 12.3% conversion rate. So far this season he has scored 25 goals from 132 shots, which works out at 18.9%.

What has driven this increased conversion?

Red Alert

Below I’ve broken down Suárez’s goal conversion exploits into matches played home and away over the past two seasons. In terms of sample sizes, in 2012/13 he took 98 shots at home and 89 shots away, while he has taken 69 and 63 respectively this season.

Season Home Away Overall
2012/13 11.2% 13.5% 12.3%
2013/14 23.2% 14.3% 18.9%

The obvious conclusion is that Suárez’s improved goal scoring rate has largely been driven by an increased conversion percentage at home. His improvement away is minor, coming in at 0.8% but his home improvement is a huge 12%.

What could be driving this upturn?

Total Annihilation

Liverpool’s home goal scoring record this season has seen them average 3 goals per game compared to 1.7 last season. Liverpool have handed out several thrashings at home this season, scoring 3 or more goals in nine of their fourteen matches. Their away goal scoring has improved from 2 goals per game to 2.27 per game for comparison.

Liverpool have been annihilating their opponents at home this season and I suspect Suárez is reaping some of the benefit of this with his improved goal scoring rate. Liverpool have typically gone ahead early in their matches at home this season but aside from their initial Suárez-less matches, that hasn’t generally seen them ease off in terms of their attacking play (they lead the league in shots per game at home with 20.7).

My working theory is that Suárez has benefited from such situations by taking his shots under less pressure and/or better locations when Liverpool have been leading at home. I would love to hear from those who collect more detailed shot data on this.

Drilling down into some more shooting metrics at home adds some support to this. Suárez has seen a greater percentage of his shots hit the target at home this season compared with last (46.4% vs 35.7%). He has also seen a smaller percentage being blocked this season (13% vs 24.5%). Half of Suárez’s shots on target at home this season have resulted in a goal compared to 31.4% last season. Away from home, the comparison between this season and last is much closer.

These numbers are consistent with Suárez taking his shots at home this season in better circumstances. I should stress that there is a degree of circularity here as Suárez’s goal scoring is not independent of Liverpool’s. Further analysis is required.

Starcraft

The above is an attempt to explain Suárez’s improved goal scoring form. I doubt it is the whole story but it hopefully provides some clues ahead of more detailed analysis. Suárez may well have also benefited from a hot-streak this season and the big question will be whether he can sustain his goal scoring form over the remainder of this season and into next.

As I’ve shown previously, there is a large amount of variability in player shot conversion from season to season. Some of this will be due to ‘luck’ or randomness but some of this could be due to specific circumstances such as those potentially aiding Suárez this season. Explaining the various factors involved in goal scoring is a tricky puzzle indeed.

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All data in this post are from Squawka and WhoScored.

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.

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.

Assessing forward involvement

One of the more interesting innovations from an analytical standpoint at the current European Championship has been the measuring of the amount of time that a player spends with the ball per game. This measure of player involvement has in particular been applied to forward players, such as Mario Gomez. Gomez managed to score 3 goals from 6 shots in 2 games despite only having the ball for 22 seconds, according to Prozone. This contrasted with Robin Van Persie, who was seemingly more involved in general play, scoring 1 goal from 10 shots in 106 seconds.

This prompts the question: can we assess such player involvement on a wider level, with particular focus on forward players?

Without having access to the time in possession statistics, another measure is required. The number of passes per game should give a reasonable approximation of how involved a forward is in general play. Contrasting this with the number of shots attempted per game should provide a comparison between a forwards goal scoring duties and his overall involvement in play.

Top European League analysis

Below is a comparison of the number of shots a forward attempts per game vs the number of passes he attempts per game. The data is taken from WhoScored.com and is for all players classified as forwards and have started 10 games or more in the top division in England, Spain, Italy, Germany and France. The graph includes players who have played in a non-forward role at some point in the season, as defined by WhoScored. For example, Cristiano Ronaldo is classified as playing as both a left-sided attacking midfielder and forward, although in this case the distinction is likely irrelevant. Including players who have at some point played outside of the forward line makes little impact upon the general trend and averages (see table below).

Relationship between number of shots attempted per game vs number of passes attempted per game by forward players in the top division in England, Spain, Italy, Germany and France. The points are coloured by the number of goals scored by each player. The vertical dashed grey line indicates the average number of passes per game by these players, while the horizontal dashed grey line indicates the average number of shots attempted by these players. The text boxes (Z1, Z2, Z3, Z4) designate the zones of interest referred to in the text. All data is taken from WhoScored.com for the 2011/12 season. An interactive version of the plot is available here, where you can find any of the forwards included in the study.

Filter Players Shots/game Passes/game Goals
Forwards only 130 2.06±0.76 18.72±6.24 7.96±5.85
Mixed 135 2.10±1.01 24.67±8.82 8.23±7.57
All 265 2.08±0.89 21.75±8.21 8.10±6.77

Comparison of the different player position classifications prescribed by WhoScored. The mean and standard deviation for shots/game, passes/game and goals scored are given for each group. Mixed refers to players who have been classed as playing as both a forward and another position (generally as an attacking midfielder) at some point in the 2011/12 season.

In general, there is a weak positive relationship between shots attempted and passes attempted by forward players (correlation coefficient of 0.46 if you are that way inclined). The major feature though is that there is a great deal of variability across the forward players in terms of their involvement in player relative to their goal scoring attempts. An interactive version of the plot is available here, where you can find any of the forwards included in the study.

Players such as Mario Gomez and Jermain Defoe take an above average number of shots relative to the number of passes they attempt (Zone 1), with Gomez in particular being prolific for Bayern Munich with 26 goals in 30 Bundesliga starts. Other notable forwards with these traits include Antonio Di Natale, Robert Lewandowski, Edison Cavani, Mario Balotelli and Falcao who attempt a slightly below average number of passes but still attempt a large number of shots per game. Fernando Llorente and Andy Carroll also reside in this zone, with similar values for shots attempted and passes attempted. Players in this zone score 9.6 goals on average.

Several “star” forwards reside in Zone 2, where forwards take an above average number of shots and attempt an above average number of passes. The two extremes here are unsurprisingly Lionel Messi and Cristiano Ronaldo, who attempt the most passes and take the most shots respectively out of all of the forwards in the study. Messi ranks 34th for the number of passes across the top five European leagues, some 30 passes behind his Barcelona team-mate Xavi. Clearly, Messi’s false-nine role for Barcelona allows him to become extremely involved in general play and to even dictate it at times. He combines this with being Barcelona’s primary provider of shots on goal and indeed goals. Ronaldo is also involved significantly in Real Madrid’s play and incredibly attempts almost 7 shots per game. Several other notable forwards in this zone include Francesco Totti, Wayne Rooney, Zlatan Ibrahimovic, Raúl, Luis Suárez and Robin Van Persie with some of these forwards being more prolific than others. Clint Dempsey is an example of someone who generally plays outside of the forward line but is included here as he did play up-front for Fulham this season (scoring 5 goals in 5 games according to WhoScored). Players in this zone score 13.7 goals on average, although this is somewhat skewed by the exploits of Messi and Ronaldo (12.6 goals on average when excluding them).

Out of the 265 players included, 98 attempt both a lower than average number of shots and passes per game. In general, the number of goals scored in this group (Zone 3) is unremarkable, with the average goals scored per player being 5. However, there is one significant over-perfomer; Gonzalo Higuaín scored 22 league goals from 60 shots last season. In most squads, this would guarantee more games but he was up against Karim Benzema, who by comparison scored a paltry 21 goals from 100 shots. However, an added benefit of Benzema based on this analysis is that he is far more involved in general play.

The last group (Zone 4) includes players who take fewer shots than average but attempt more passes than average. Many of these players are more attacking midfield players than forwards, such as Dirk Kuyt. Again, a Fulham player is a good example of a player who rarely plays as a forward being included in the analysis, as Moussa Dembélé generally plays in midfield. Players in this zone score 5.3 goals on average, essentially the same as those in Zone 3.

Finishing the jigsaw

Clearly there is a large variation in how involved a forward player is in general play versus how often he attempts to score. Such differences are likely driven by both the individual player in terms of their skills and style of play alongside their tactical role within the team. Mario Gomez for instance has very similar numbers from the current European Championship for Germany as he does for his club side, although this could be a statistical quirk given the small sample size. It would be interesting to analyse how an individual performs by these measures across multiple games in multiple tactical systems.

There isn’t necessarily a better “zone” in this analysis but teams should bear these traits in mind when attempting to improve their squad. For example, Liverpool’s woes in front of goal last season led for calls for a simple poacher to be brought in who would simply “stick the ball in the net”. However, if by bringing in a poacher, Liverpool were to lose the passing and creativity provided by players in other areas, then you could end up exchanging one problem for another. Balance is key in such decisions; hopefully Brendan Rodgers can solve Liverpool’s goal scoring issues and at least maintain the quality of their chance creation next season.