Thursday, 1 March 2012

Skilful Passing Teams in the EPL.

In American Football field position is paramount.If your team has a 1st and 10 on their opponents 35 yard line they can expect to come away with around three points over the long term.About a third of the time your team will break the whitewash for a touchdown,a quarter of the time they'll have to settle for a field goal and the rest of the time the ball will be turned over without a score.It's therefore understandable that efforts are being made to try to establish the importance of field position in football or soccer if you prefer.However,the case of soocer/football may prove to be a much harder nut to crack.

The NFL is essentially a sequence of 60 or so individual plays,where each offense and defense is allowed to re group and prepare itself at the start of each play or down.By contrast a soccer team can arrive at a position on the field through steady build up play,where they find themselves confronted by a well manned and organised defence or they can get to the same spot via a rapid break,pulling a desperately retreating defence out of position and possibly outnumbering them in the process.In the former case the defence will probably feel fairly comfortable with their position,in the latter the attackers have the upper hand.The same field position in both cases,but a widely differing chance of a goal.

How you arrived at your field position is virtually irrelevant in the NFL because the game restarts from where the ball carrier is tackled,but that's not the case in soccer,where field position can be simply one point in a fluid journey that only ends when the ball is turned over.Arriving at an advanced position on the field in the quickest time can give the attacking side a huge advantage over teams who aren't as adept at quickly transferring the ball from one player to another and ideally anyone interested in football analysis would like a way of expressing this team ability.Therefore,the techniques used to analyse field position in the NFL aren't well suited to use in football/soccer.We need to know what might happen after the running back makes his first cut,and current NFL type analysis only really tells us what might happen after he's been tackled.

The development of attacking moves in soccer is usually dealt with by visual analysis,but this is both time consuming and impractical for most casually interested fan.So hot on the heels of witnessing Valencia's quickfire one touch counters and Stoke's more ponderous build up in the Europa Cup I tried to come up with a useful statistic to describe a team's attacking tendencies and the kind of defensive disruption their attacks can cause.

In sports analysis rate measurements are usually much more potent that simple counting or measuring.Passes are the building blocks of attacking moves and the number of times a player touches the ball can be the prelude to attempting a pass.If we divide the number of times a player or team touches the ball by the number of passes they make,we can begin to see which teams are ponderous on the ball and which teams fire the ball quickly around the pitch.An extra touch can be the difference between a defender chasing shadows or effectively closing down a forward.The numbers available at the moment aren't perfect, because they include all touches and not just those made during the reception of a pass and the completion of a subsequent pass,so the subsequent analysis should be treat with caution.

If we now plot a team's touch per pass ratio against pass accuracy we can see how many teams possess the potent mix of a quick "one touch" approach and good accuracy.

Remarkably,there appears to be an extremely strong correlation between teams who need fewer touches before delivering a pass and that team's accuracy.The most accurate teams also need fewer touches before delivering the pass.Arsenal,ManU,Chelsea,Liverpool and Tottenham occupy spots in the top left hand and Blackburn,Stoke,Hull,Birmingham and Bolton tend to inhabit the bottom right of the graph.If we continue to plot correlations,we find that the more accurate a team's passing then generally the more goals they score in open play.

The strength of this correlation isn't as strong as the previous one,but the narrative is starting to make uncomfortable reading for teams who inhabit the lower regions of the EPL table.The most expensive and best players from the top teams appear to be able to pass the ball quickly and accurately,(call this skill,if you like) this leads to more goals from open play and more goals correlates with a higher final position.Team's with less expensive and less skilful players need more touches to effect their passes and they are less accurate as well.This leads to less goals from open play per game and condemns them to a lower final league position.

One way these teams can increase their goals tally by scoring from set plays,but as the next graph shows,goals scored from set plays appear to be a non repeatable skill.

 The season to season correlation between the number of set play goals a team scores is essentially zero and a large number of such goals in one year cannot be relied upon to appear in subsequent seasons.Randomness can conspire to keep a less skilful team in the Premiership one year,but fail them in later years when they may have to rely one their skilfully created goals from open play.

The second way less skilful teams can try to survive the EPL experience is through good,well organised defence and anecdotally you could suggest that Tony Pulis at Stoke made this his approach in the Potters first two seasons.Defence was at the forefront of many performances in Stoke's first two season in the Premiership and in Delap they had that rare commodity,a partly repeatable set piece skill.

The usefulness of the Touches per Pass stat will have to wait for more context to be applied to the raw numbers,such as current score and possibly a player based rather than simply a team investigation of data.But for the moment it does a reasonable job of combining two of the more recent additions to the slew of new numbers that are being made available at such sites as EPL Index.And hopefully creates a new one that adds value.

(There is also a very plausible explanation of these results where it is the game result that causes the apparent need for poorer teams to take more touches to complete a lower percentage of passes.So it's slightly premature to crown Man City as a team of one touch,super passers.This kind of approach also throws up the possibilities of a passing unit only being as good as it's weakest link ....but I'll leave that for another day).    

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