Friday, 2 September 2011

The Myth of the Clutch Goalscorer.

EP would appear to be the ideal tool to investigate whether a player has the ability to score high value goals almost on demand.However,before we imbue players with a special talent we first have to determine whether or not clutch ability exists in the first place.

It's very easy to take incomplete or sparse data and make seemingly logical leaps of faith to produce incorrect conclusions.Teams are often seen to be draw specialists using reasoning based on little more than one seasons worth of results during which a team draws a lot of games.However, if you look at enough teams you're almost certain to to see one set of results that are far enough from the usual average to justify the use of the specialist tag,when all you are really seeing is perfectly natural random variation.For the tag to be legitimate we need to be seeing the phenomena persist for many seasons.

Draw specialists are almost never that.If you take the teams who drew the most games in one season and then average those teams draws in the subsequent season you'll find that the figures always return to the league average.

Home or away specialists also go the same way,with maybe one or two very special exceptions.

So to make answering the clutch question more palatable I propose to firstly see if it's possible to identify any teams that exhibit the trait.Are they more likely to score goals that are important to the match outcome and does this ability persist.

The average goal difference per game for a team is a very good indicator for the number of points a team will achieve over he course of a season.In general terms for every 0.1 increase in goal difference a team will increase it's average points per game by 0.066 of a  point,put formally a team's goal difference per game multiplied by 0.66 plus 1.37 gives the average number of points per game a team will gain in the EPL.

Average Points Per Game = 0.66 * (average goal difference) + 1.37

If we therefore calculated the number of points that a team would have expected to gain over a season given it's goal difference and compare that to their actual points haul we can see which teams are out performing their goal difference.We can see which teams are scoring lots of important goals as opposed to lots of scoreline boosting ones.

As with so called draw specialists mentioned previously it's important the recognise that one season out performing the trend line doesn't make a team a clutch scoring side,natural variation is to be expected.We are looking for teams to continually out perform over a consistent series of seasons and then,just as crucially we need to try to identify any factors that support the designation we've given them.

The results would seem to suggest that teams can not consistently beat the goal difference by scoring a larger than expected number of important goals.Manchester United are fairly typical of the sample,over the last twelve seasons their points total over performed against goal difference on 7 occasions and underperformed on 5.Newcastle split 5 against 6 and Sunderland 5 against 4.Wolves have overperformed on each of their 3 premiership seasons,but even this has about a 1 in 7 chance of occurring by luck alone.

So clutch teams would appear to be rare if they exist at all.It's hard to imagine a reason why for example Wolves might be one.They are a fairly unremarkable EPL side,although one clue might lie in their astute manager who clearly prioritises winnable games.So perhaps apparent overperformance could be a trait of the manager.

If we look at Chelsea's record it at first glance appears fairly average.Their split is 7 and 5 in favour of overperformance.However,there is a run of three seasons in the mid 2000's coinciding with  Mourhinio's reign when they overperformed by around 5 league points in each of those 3 years.Pre and post Mourhinio they had been a 50:50 split side.

If we delve deeper into Chelsea's record we find that they were indeed more likely to score vital goals at vital times.The chances that a team scores the next goal is strongly tied to their chances of winning the game and so it is with Chelsea.If a next goal was scored in the Mourhinio years there was a 77% chance that Chelsea would score it.However,when Chelsea trailed or the game was tied (other than 0-0's) then the chance that the next goal would come from Chelsea was in excess of 87%.It could be argued that Mourhinio made tactical changes when trailing or drawing late in the game that made scoring more likely,his team carried this out and then together they cemented the gains made by these high EP goals and that was reflected in the final table......or he and they could have been lucky,3 consecutive "up" seasons are still just a 1 in 7 random event.

Except he then did the same in his 2 years at Inter,bringing the total to 5 consecutive seasons,one chance in 32 by luck.

If we look at the EP for all of Chelsea/Morhinio games,we'll probably find a Chelsea player who appears clutch because he scores a higher proportion of important goals.But the truth is possibly more complex.He more likely scores more vital goals because the team embraced the tactical changes,upped their game pace to higher but ultimately unsustainable levels (a very common and obvious occurrence near to the interval in rugby for example) and gave him greater opportunity to score.

If it exists,it's a team and manager trait.

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