Plus-Minus Follow Up

Just following up on yesterday's article regarding plus-minus. Plus-Minus is a useful tool to see how a player played in relation to the rest of his team, but should not be considered an official ranking of players on the roster.

In fact, soccer plus-minus must be taken with a large grain of salt because of sample size issues. In other sports, basketball and hockey, there are much larger sample sizes to work with because of the number of points accumulated in those games. When working with small sample sizes like the below article, we must understand that they numbers give us a small insight into player performance, but does not fully encompass a players impact on the team. Certain players are helped by situations out of their control while others suffer due to team circumstances that they play no part in. Let's take a look at Eduardo, who had questionable results from the 2009 season:


Eduardo: Eduardo's +/- per 90 minutes of 1.77 was tops among regular players for Arsenal in 2009. Simply put, Arsenal outscored their opponents by 1.77 goals for every 90 minutes Eduardo was on the pitch. Most Arsenal supporters would say how can that be? We all know Eduardo struggled to regain the form after the leg break in February 2008 and only netted twice in 24 appearances for Arsenal in 2009. Well Eduardo's strong +/- is due to circumstances of late match substitutions more-so than his individual abilities. Eduardo started 13 matches and came in as a sub 11 times. In the 13 matches that Eduardo started in, he played 945 minutes and Arsenal had a +/- of +16. In the 11 matches which Eduardo was a sub, he played 176 minutes and Arsenal had a +/- of +6 in that time. Look at this chart:

Eduardo	+/-	Mins	+/- per 90
Started	16	945	1.52
Sub	6	176	3.07

Eduardo had a +/- per 90 minutes of 1.52 while he was a starter, but an amazing 3.07 coming in as a late match sub. Eduardo's +/- has less to do with his own ability and more because of Arsenal's ability to score late goals. Without looking hard at other players, my guess would be strikers who come on as late subs will often see this happen. By virtue of playing a lot of late minutes, Eduardo was helped by Arsenal's ability to score at the end. Here is Eduardo's match log from the 2009 season:

Fixture	Result	+/-	Start/Sub	Min
1	W	0	Sub	73
2	W	3	Start	71
3	L	0	Sub	79
4	L	(1)	Sub	77
5	W	3	Start	74
6	W
7	W
8	W
9	D	0	Sub	88
10	W	3	Sub	37
11	W	4	Start	71
12	L	(1)	Start	71
13	L	(2)	Start	57
14	W
15	W
16	D	0	Sub	64
17	W	2	Start	75
18	W	0	Start	64
19	W	3	Start	72
20	D	0	Start	75
21	W	2	Start	84
22	W	2	Start	90
23	D	0	Start	62
24	L
25	L
26	W
27	W
28	W	2	Sub	84
29	W	1	Sub	74
30	W	1	Sub	76
31	W	0	Sub	84
32	D
33	W	0	Start	79
34	L
35	L
36	D
37	L	0	Sub	78
38	W