Last summer, Manchester City’s Head of Performance Analysis Gavin Fleig made a bold decision. In an effort to advance the concept of advanced statistics in soccer, Fleig decided to make City's advanced scouting data public for anybody who requested it.
Fleig’s reasoning was simple: if teams continue to keep this information all to themselves, there is a chance that they will miss out on the opportunity to advance the game as a whole, and potentially revolutionize the way that business is done. As Fleig told the Guardian, “Somewhere in the world there is football's Bill James, who has all the skills and wants to use them but hasn't got the data. We want to help find that Bill James, not necessarily for Manchester City but for the benefit of analytics in football.”
Paritally because of Fleig, the conversation about performance data is beginning to evolve, particularly with data companies like Opta leading the way. Here are a few stats that are starting to become more accepted within the soccer community.
Key Passes are defined as passes that lead to a shot attempt, and/or a quality scoring opportunity. This stat is obviously important for midfielders, but it has changed the conversation about the value of strikers as well.
A great example of this is PSG Striker Zlatan Ibrahimovic. The towering striker is recognized as a pure scorer, and has netted 24 goals this season (most in Ligue 1). But an underrated facet of his game is his passing, and in addition to his finishing prowess, his 46 key passes this season are the most on his league-leading PSG side (data from WhoScored).
When Liverpool signed winger Stewart Downing and striker Andy Carroll before the 2011/2012 season, the perception was that this was the beginning of the ‘Moneyball’ era.Boston Red Sox and Liverpool owner John Henry saw a (seemingly) underrated winger who was an efficient crosser, and paired him with a (seemingly) underrated striker who would be a big target in the box.
The experiment did not go as well as planned, but it did make more fans pay attention to the crossing ability of wide players, and for that matter the finishing ability of target strikers, specifically from crosses.
Two years later, the advanced analysis of crossing accuracy may actually show that it is somewhat of a dying art. According to EPL Index, the two most accurate open play crossing EPL teams, West Ham and Norwich City, rank 18th and 16th respectively in goals scored. And if you subscribe to the theory that many teams hope to one day emulate Barcelona, it is important to note that they have little use for crosses, averaging just 15 attempts per game.
The ability to complete passes has always been an essential quality for a good midfielder, but only recently have we begun to see a player’s pass success rate displayed regularly in broadcasts. This statistic shows not only how effective a midfielder can be going forward, but how versatile a team can be with a defensive midfielder who can also move the ball (i.e. Sergio Busquets, Mikel Arteta).
Not surprisingly, Barcelona dominates in this category, and have players that occupy each of the top 10 ten rankings in La Liga pass completion. The style of Barcelona, and other teams that mirror them, may skew the importance of pass success percentage, but regardless it is an advanced statistic that has opened the door to new theories in player evaluation.
There are plenty of teams out there that excel in possession, but there is an increasing curiosity among soccer fans about how useful possession is. Attacking third passes are slowly becoming more integrated in soccer discussions, and are an important way of distinguishing the effectiveness of a team’s ability to possess the ball.
By measuring passes in a specific part of the field, fans are able to disregard a team’s ability to pass the ball in its own half of the field. For example, Swansea prides itself on ball possession, and ranks fifth in the EPL with 55.8 percent per game.
However, 29 percent of that possession happens to be on Swansea’s own half of the field, which could explain why they are not the imposing force that their possession suggests they are (data from WhoScored).
This season, Robin Van Persie and Zlatan Ibrahimovic have proven that a premier striker can be an invaluable addition, and clubs are always on the lookout for that player who can change the course of a game with his exceptional finishing ability.
Chance conversion rate simply measures the ratio of a player’s shot attempts to goals, and has become a popular measure of not just player efficiency, but team efficiency as well. For advanced statisticians, it is a great starting point for comparing players, and opens the door to comparing entire teams.
For example, if Luis Suarez has scored 22 goals at a 13.9% conversion rate this season, is he having a better season than Robin Van Persie, who has 19 goals and a 19.4% conversion rate? (stats provided by Opta)