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Graph: 2010/11 Premier League Shot Volume vs Efficiency

July 10, 2011 1 comment

Below is a graph of the goals per shot and shots per 90 minutes ratios of every player who took 40 or more shots in the 2010/11 Premier League season.

Data Sources: http://www.telegraph.co.uk/ and http://www.football-lineups.com/

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Categories: General

Goalkeeper Performance in England, Spain and Germany

April 13, 2011 4 comments

I have written in previous posts about the importance and value of shot stopping. So how have goalkeepers in the real world done so far this season?

I collected data on the current Premier League, La Liga and Bundesliga seasons from Sports Illustrated’s website and put it all together into the following graph. The data includes every match played from the start of the season to April 13th. Note that I included only goalkeepers who have played at least 1500 minutes.

Shots On Target Conceded vs Goals Conceded

In the following table I have listed every goalkeeper’s goals allowed, shots on target faced, minutes played, saves made and EV Diff, which is a measure of how much a goalkeeper has over- or underperformed relative to expectation based on how many shots on target they have faced. Ben Foster’s 18,46 goals means he has conceded 18,46 goals fewer than would have been expected based on how many shots on target he has faced. Scott Carson on the other hand has conceded 12,73 goals more than expected.

Player GA SOT Mins Saves EV Diff
Foster 43 198 2790 156 18,4555833
De Gea 41 165 2790 124 8,682483054
Hart 30 134 2880 104 8,622904031
Baumann 33 142 2250 108 8,47698894
Cech 25 119 2790 95 8,271494827
Calat’d 45 175 2689 125 8,25008919
Kameni 38 152 2430 114 7,044595077
Ricardo 37 146 2790 107 5,904031395
Gomes 31 129 2340 98 5,839100963
Alves 54 192 2790 139 5,315019622
Neuer 33 133 2610 101 5,266143418
Jääsk’n 38 147 2646 108 5,260792009
Valdes 14 79 2430 65 5,001070282
Begovic 29 119 2070 91 4,271494827
Weide’r 17 84 2520 68 3,78487335
Lopez 36 137 2790 100 3,693185872
Green 55 189 2790 135 3,244737781
M Reina 25 103 1620 79 2,563325009
Schwa’r 29 114 2250 86 2,487691759
Wetklo 18 82 1645 64 2,071352123
Toño 45 157 2790 106 1,828398145
Aranz’a 29 110 2250 81 1,060649304
Bravo 54 180 2790 125 1,033892258
AlHabsi 40 139 2520 98 0,4067071
VDS 28 105 2520 78 0,276846236
Casil’s 22 88 2612 67 0,211915804
Migno’t 24 93 1530 69 -0,004281127
Benag’o 33 118 2049 85 -0,085265787
Codina 33 117 2054 80 -0,4420264
Aouate 42 142 2700 94 -0,52301106
Robin’n 48 158 2655 110 -0,814841242
Pablo 23 86 1642 62 -1,501605423
Friedel 53 167 2880 114 -2,603995719
Iraizoz 45 144 2790 97 -2,809489832
Reina 38 124 2880 87 -2,944702105
Kessler 39 126 2048 87 -3,231180878
Ulreich 54 166 2610 113 -3,960756333
Palop 28 91 1632 61 -4,717802355
Kingson 38 119 1698 81 -4,728505173
Sippel 42 130 2250 89 -4,804138423
Howard 41 126 2880 88 -5,231180878
Nikolov 28 89 1755 61 -5,431323582
Henne’y 31 97 1620 66 -5,577238673
Adler 32 99 2430 69 -5,863717446
Rost 36 110 2203 76 -5,939350696
Starke 29 90 1800 62 -6,074562968
Schäfer 37 112 2579 75 -6,225829468
Harper 22 68 1565 46 -6,923296468
Wiese 45 131 2158 88 -7,447377809
Butt 21 63 1575 43 -7,707099536
Franco 30 84 1671 55 -9,21512665
Froml’z 34 94 1748 61 -9,647520514
Carson 46 119 2340 75 -12,72850517

Clearly this analysis isn’t perfect. For starters it considers all shots as equal, which clearly isn’t true. Some shots are more difficult to save than others, and some goalkeepers will have faced relatively more difficult shots while others will have faced relatively more easy shots. For example, has Petr Cech really performed 8,27 goals above expectation or has he just faced a disproportionately large number of easy shots which serve to make it look like he has performed better than he actually has? I don’t know. Certainly these numbers shouldn’t be taken as gospel and should instead be thought of as a supplement to your eyeball test when evaluating goalkeeper performance. But perhaps they are useful, if for no other reason than to get people to think about why they may not be an accurate representation of reality and what could be done to improve on them.

Categories: General

The Need For Objectivity

February 14, 2011 1 comment

“Men act like beasts insofar as the sequence of their perceptions results from the principle of memory alone: they resemble the empirical physicians who practice without theory.” Gottfried Leibniz

Over the past few months I have become increasingly frustrated at the lack of objective analysis in football. Almost all football debate be it in the pub or on the internet inevitably devolves into a game of this is my opinion and this is your opinion, let’s see who can shout the loudest. Bonus points are awarded for insulting your opponents, having the highest word count and never admitting you’re wrong.

The most common method of player evaluation is the subjective and unreliable eyeball test. You watch a match involving 22 players where often you will be rooting for one of the teams or one of your favourite players to do well, most of the time you will be focusing on the player with the ball and ignoring what happens around him, and by the end of the match you will probably already have forgotten most of what happened at the start. All this is then passed through the filter of various biases in the brain which we know is notoriously poor at evaluating events objectively. The end product is a hodge-podge of incomplete data seasoned with all your favourite biases and predetermined notions of how you think things are supposed to work, and this is what you use to draw your conclusions from. The limitations of this method are obvious yet rarely if ever will you see someone question it, instead we all have an unspoken agreement that this is the way it has always been done and this is the way it should be done.

There is a need for objectivity in football analysis. The use of statistics and mathematics in addressing problems of player evaluation, team evaluation, and on- and off-pitch situations in football is still at an elementary level when compared to other sports like baseball and basketball but I feel strongly that it is the only way we can move football analysis away from the clutches of subjectivity and into the warm embrace of well-reasoned, logically sound objective argument. That isn’t to say that these methods don’t have their limitations and weaknesses, and certainly football presents a unique set of problems that sports like baseball or American football don’t have to deal with, but rather than shying away from them we should be tackling them head-on in an attempt to move the level of football analysis away from the age of cavemen and into the modern era.

Nonetheless it is an unavoidable fact that the eyeball test is still a vital part of the way we evaluate and analyse football. Despite growing popularity the football analytics movement is still in it’s infancy and it will be a while before we have the tools to answer truly meaningful questions about the game without having to rely on the eyeball test. Until then the best we can hope to do is supplement our subjective assessment with statistics and mathematics and constantly audit our thought processes for faulty logic and inconsistencies. As Leibniz wrote: “we are all mere Empirics in three fourths of our actions.” If we could get that down to one half or one fourth then at least we will be moving in the right direction.

Categories: General