The Plus and Minus of Things

I am a big believer that in soccer everyone on the field has some type of impact on almost every play. That is why I love looking at the MpTG stat so much. As the season goes on and there becomes a greater sample size, it shows a good representation on how well the team plays offensively while that particular player is on the field. Plus or minus (+/-) stats are another indicator of how well the team does when particular players are on the field.

At one point in the season someone asked me if I tracked +/- stats for players. At that time I did not, but I could see the value in it. I went back and calculated the stat and found some very interesting results. I have been keeping track of it ever since.

Historically +/- has been something that hockey teams have tracked. It has been only recently that it has moved to other sports like basketball. What is +/-? It is goal differential on a player level instead of a team level. You take all the goals that have been scored while a particular player is on the field and then subtract the amount of goals that have been given up while that player is on the field. Unlike MpTG the higher the number the better. I thought it would be good to take a look at the players current +/- and see what information we can learn from it.

RSL's goal differential is currently at +17 for the season. Lets first take a look at the forwards.

Player	Min	+/-
Saborio	1081	4
Findley	1070	5
Plata	1397	12
Sandoval	704	10
Garcia	831	7

So what can we tell from this? Theoretically, the more minutes a player plays, the closer his +/- will get to the team's differential for the season. I find it interesting that Sandoval has the second best +/- and has played the least amount among all the forwards. It is also interesting that Garcia who has by far the best MpTG on the team only has an average +/-. I am not sure what it means that Saborio and Findley have low +/- numbers. 

Player	Min	+/-
Gil	1625	9
Grabavoy	2220	17
Morales	1976	20
Velasquez	802	9
Stephenson	717	0
Beckerman	1831	17
Alvarez	747	4
Grossman	88	1

Above are the stats for the RSL midfielders. Morales stands out in this group with his +20. This is the highest on the team. It is interesting that Velasquez has played almost exactly half the amount of minutes that Gil has but they have the same +/-. And, what does it say that after playing over 700 minutes that Stephenson's +/- is still at 0?

Player	Min	+/-
Beltran	1879	19
Schuler	1080	0
Borchers	2070	16
Salcedo	901	14
Palmer	940	-7
Mansally	669	3
Watson-Siriboe	630	3
Maund	270	-1
McDonald	180	0

Finally here are the defender's stats. Beltran's +19 is outstanding as only he and Morales have numbers that are higher than the team differential. Salcedo really jumped out to me as well. For only playing 900 minutes his +14 is very impressive. On the flip side is Palmer. The team has really struggled defensively when he has played this year. 

What else can we figure out from these stats? I would love to hear what any one else thinks about it.