Stats: 2011 MLS Player +/- Rankings

Soccer stats tend to fall into two categories. There are the stats that are easy for the casual fan-slash-statistician to observe and tally, but which are almost hopelessly uninformative. That would include goals, assists, minutes played, and so on. Then there are the stats that provide significantly more insight but due to the continuous nature of the game take dedicated resources to measure. That would include time of possession, passing percentages, distance traveled, success rates in various zones of the pitch, etc.

The sweet spot lies somewhere in the middle. Ideally you would have a set of stats that lend themselves to insights about the game and players but don't require tracking the precise location of every game event. One stat that we're working on maintaining is +/- (or Plus Minus). Hockey fans will be well aware of the stat, which keeps track of the net goals scored (that is, goals scored minus goals allowed) while a player is on the ice. NBA +/- is also tracked by basketball stat geeks. In both cases it helps track the contributions of a player whose job isn't necessarily scoring directly but who influences the scoring outputs of the teams one way or another. Adapting the stat to soccer is just a matter of keeping track of substitutions to know when players are on the field.

I've also decided to focus on shots rather than goals. As we've explored here before, there's few enough goals in a match that it takes a much larger sample size to shake out random effects. So instead we'll measure the shot differential while a player is in the game. But even so you'll find that players on the same team will tend to cluster together. Substitutions in soccer are much rarer in both basketball and hockey, where players cycle into and out of the game regularly. Instead it may take many months or a full season before there's little enough overlap between players on the same team that the results are completely distinct. But even this far into the season there are players that stand out.

Here is the top 10 Shot +/- per 90 minutes played through Wednesday's games:

Rank	Team		Player	Shot +/-
1		Real Salt Lake	Fabian Espindola	5.24
2		Houston Dynamo	Cam Weaver	5.07
3		Real Salt Lake	Ned Grabavoy	4.74
4		New York Red Bulls	Thierry Henry	4.70
5		New York Red Bulls	Dan Richards	4.70
6		New York Red Bulls	Luke Rodgers	4.63
7		Columbus Crew	Emilio Renteria	4.59
8		Columbus Crew	Robbie Rogers	4.39
9		New York Red Bulls	Rafa Marquez	4.20
10		New York Red Bulls	Tim Ream	4.20

The heavy New York representation is indicative of a team that significantly outshoots its opponents. It's also interesting that Columbus is well represented. Both Columbus and the Philadelphia Union are considered defense-first teams that are getting success by grinding out low-scoring wins, but most people don't notice that the Crew are second in the league in net shots, while Philadelphia are third from worst (ahead of Chivas USA and Toronto FC). Based on that, I'm guessing Columbus' success in the standings may be more long-lived than Philadelphia's.

And here's the top Plus Minus player for each team:

Team		Player	Shot +/-
	Real Salt Lake	Fabian Espindola	5.24
	Houston Dynamo	Cam Weaver	5.07
	New York Red Bulls	Thierry Henry	4.70
	Columbus Crew	Emilio Renteria	4.59
	Seattle Sounders FC	Brad Evans	3.54
	LA Galaxy	Chad Barrett	2.87
	Chicago Fire	Josip Mikulic	2.77
	Portland Timbers	Mamadou Danso	2.40
	FC Dallas	Fabian Castillo	2.40
	Sporting Kansas City	Julio Cesar	1.63
	Vancouver Whitecaps	Terry Dunfield	1.28
	New England Revolution	Didier Domi	0.00
	DC United	Perry Kitchen	-0.19
	Colorado Rapids	Pablo Mastroeni	-0.30
	San Jose Earthquakes	Ryan Johnson	-0.73
	Chivas USA	Jorge Flores	-0.97
	Philadelphia Union	Carlos Ruiz	-2.09
	Toronto FC	Tony Tchani	-3.11