Thursday, June 27, 2013

Who's the Best Passing GK in the EPL?

Is passing % an intuitive starting point?  Not really, because while such a proxy might work with outfield players, goalies are a bit unique in that the majority of their passes are of a binary nature: long hopeful balls (either from the run of play or goal kicks) or short passes to a usually-unmarked defender.  Across the EPL, the average goalie's passing % on long balls is 40%  while their average passing % on short passes is 90%.

As such, you must also consider how the composition of pass type (long/short) varies between goalies.  Only 6.2% of Adam Federici's total passes attempted were short while, on the other end of the spectrum, 45.5% of Michael Vorm's passes were short.  Below is a table illustrating the different passing style of each EPL goalie.  This is sorted by overall passing %.

A couple things immediately jump out. One is the direct relationship between the % of short passes and the short passing%.  This is interesting, though somewhat intuitive:  the fewer short passes a goalie attempts the lower their completion percent; they are likely under defensive duress, which is the same reason why the majority of their passes are long balls.  

I ran a regression between a player's overall passing completion % and the % of their passes that were long/short.  The idea is simple: the more long passes you attempt relative to short passes the lower your overall passing %, and vice versa.  The relationship was quite strong for only 20 observations.

Regression Statistics
Multiple R 0.846737
R Square 0.716963
Adjusted R Square 0.701239
Standard Error 0.051857
Observations 20

With regression in hand, the next step is figuring out which goalies over and under-performed their expected overall passing completion percentage with a crude predicted pass completion % model.  Here are the EPL goalies ranked from best to worst passer. Begovic is the best over-performer and Julio Cesar is the biggest under-performer.  

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