Wednesday, November 14, 2012

Back To Basics: Who Touches The Ball?

The ball is round, Sepp Herberger, the legendary, World Cup-winning coach of the 1954 West German side used to say. Moving the leather around the pitch is what football is all about. While that's always been true, how teams have gone about maneuvering the ball into their opponent's net and away from their own has changed considerably since Herberger's days, however.

In this day and age, it is hard to imagine teams playing a 2-3-5, the most common formation in the early days of the game. Instead, as Jonathan Wilson has described so beautifully in his magisterial history of football tactics, Inverting The Pyramid, football has evolved to become a game focused mostly on offense to a game focused on balancing offensive and defensive needs. Today, with the rise of the false 9, Barcelona and Spain are even occasionally playing without a striker, period.

So who touches the ball in the modern game? Is the tactical focus on a balance between offense and defense reflected in the match data?

To see if it is, we calculated which positions actually see more and which see less of the ball with the help of Opta Sports match data for a recent season of Premier League play (2010/11). Our original intuition was that the balance between offense and defense should mean that midfielders would touch the ball the most.

Here is, first, the average number of ball contacts by position and match. Touches on the ball can be anything here - passes, flick-ons, headers, shots on goal, you name it.

These numbers suggest that the average defender touched the ball significantly more than the average forward, with midfielders somewhere in the, well, middle. But what's perhaps most noticeable is that the average 55 ball contacts defenders make tower over the average 30 touches forwards get. Thus, according to these calculations, midfielders and defenders touch the back many more times than the guys tasked with putting the ball in the other side's net.

Could that be right? Has the pyramid really been completely inverted, with defenders dominating today's game?

These averages can be deceiving, and for two simple reasons. One could be tactical; the averages may hide significant variation because different formations ask different things of players. When teams play 4-5-1 rather than a 4-3-3, for example, opportunities for forwards to make contact with the ball are simply fewer.

The numbers bear this out, at least in part. For instance, in the 2010/11 season, forwards had an average of 32 touches per match when their team played a 4-3-3 formation and 25 touches when the formation was a 4-5-1. At the same time, however, we don't see these differences on the defensive side of the pitch. There, defenders had an average of 56 touches per match in a 4-5-1 and 58 in a 4-3-3 system. 

How could this be?

The reason has to do with playing time. It turns out that forwards, on average, play the fewest number of minutes per match, at slightly less than an hour on the pitch. In contrast, goalkeepers almost always play the full 90 minutes, followed by defenders at slightly over 80, and midfielders at around 70 minutes.

This difference in time spent on the field depresses the average touches for the average forward. So to get a clean picture, we need to adjust for the number of minutes played by calculating the average number of ball contacts per 90 minutes of play. And when we do that, the picture changes. Now, players of different positions aren't as radically different as they were before. Sure, forwards still touch the ball the least, but they're not longer as different from the rest. Moreover, midfielders now emerge as having the most touches on the team. This is a picture of balance in the modern game, with midfielders as the linchpins of the action.

Of course, the next big question is what it is that players do with the ball when they have a  chance to influence its direction. One of the things strikers get paid for, of course, is to score. And that is what they do, no matter how we measure it. When we calculated the number of goals per 90 minutes for each position, forwards come to the fore, yet again. Their strike rate is almost 8 times that of a defender and about 3 times that of a midfielder. 

Not bad for a position that touches the ball the least of all - even less than the goalkeeper; but that and some other interesting patterns in these data are for a future post.