MLS--fun with the team statistics and the poisson distribution

[JG]

On the thread that inspired the formation of this forum, we discussed ways to predict team records from their goals scored and goals against. It was determined that using a Poisson distribution for goals would work well.

I did some playing with this year's MLS records...here's what I found.

First I compared each teams actual points to their predicted points:


Team GF GA Pts PrPts Diff
Chicago 53 43 53 47.91 +5.09
MetroStars 40 40 42 41.10 +0.90
New England 55 47 45 46.60 -1.60
DC United 38 36 39 42.36 -3.36
Columbus 44 44 38 41.31 -3.31
San Jose 45 35 51 48.08 +2.92
Colorado 40 45 40 37.87 +2.13
Kansas City 48 44 42 44.02 -2.02
Los Angeles 35 35 36 40.78 -4.78
Dallas 35 64 23 24.22 -1.22




"PrPts" is predicted points.

The average error of 2.7 points is comparable to what I've gotten with European leagues.

Next, I compared each teams predicted record to their predicted record if they had scored/allowed a league average amount of goals (43.3), generating a number for how many points their offense and defense had earned of lost...for example, Chicago
won just over two games by scoring 53 goals instead of 43.3.

Team Off Def
Chicago +6.45 +0.20
MetroStars -2.34 +2.16
New England +7.67 -2.36
DC United -3.83 +4.87
Columbus +0.49 -0.45
San Jose +1.18 +5.64
Colorado -2.31 -1.07
Kansas City +3.20 -0.45
Los Angeles -6.11 +5.50
Dallas -5.25 -11.07




By comparing the amount of goals scored above/below the league average with the offensive rating in the above table, we can get the amount of "goals per win" for each team--for example Chicago scored 9.7 goals above the league average, which helped their team earn 6.45 points. 9.7/6.45*3=4.51 goals per win.

Team Off Gls GPW
New England +7.67 +11.7 4.58
Chicago +6.45 +9.70 4.51
Kansas City +3.20 +4.70 4.41
San Jose +1.18 +1.70 4.32
Columbus +0.49 +0.70 4.29
Colorado -2.31 -3.30 4.29
MetroStars -2.34 -3.30 4.23
DC United -3.83 -5.30 4.15
Dallas -5.25 -8.30 4.74
Los Angeles -6.11 -8.30 4.08



"Gls" = goals scored vs. the league average.
GPW = goals per win.

So an MLS team needs to score 4-5 extra goals over a season to win another game...with the exception of Dallas the higher-scoring teams need to score a bit more to win another game. For defenses the numbers are a bit higher, but still between 4 and 5 goals needed to make a one-game difference.

[JG]

Formatting tables is fun.

[superdave]

Originally posted by JG
So an MLS team needs to score 4-5 extra goals over a season to win another game...with the exception of Dallas the higher-scoring teams need to score a bit more to win another game. For defenses the numbers are a bit higher, but still between 4 and 5 goals needed to make a one-game difference.
Please clarify something. Bill James found in the 80's (with the offensive explosion since then, the numbers probably don't still hold) that a team needed to get 10 extra runs to move up a full game over .500. By that I mean, if you outscore your opponents by 20, you expect to go 83-79, NOT 82-80. When you talk about winning an extra game, do you also mean NOT LOSING an extra game? If you outscore your opposition by 9, will you win 2 more games than you lose, or 4?

It's probably obvious from your chart, but I don't have the statistical background for that. Anyway, if in my example it's 4 games, that sounds about right to me, but I'm still a bit surprised the number isn't lower. If it's 2 games, then I'm really surprised.

[beineke]

Originally posted by JG
So an MLS team needs to score 4-5 extra goals over a season to win another game...with the exception of Dallas the higher-scoring teams need to score a bit more to win another game. For defenses the numbers are a bit higher, but still between 4 and 5 goals needed to make a one-game difference.

Great work ... IMO, this is a very interesting result. Intuitively, I would've thought that fewer goals would buy you an extra win.

At some point, I'd like to go back to those save percentages and see how much of a difference a good shot-stopper might make.

[JG]

Originally posted by superdave
When you talk about winning an extra game, do you also mean NOT LOSING an extra game?

Yeah, that's what I mean...a team that outscores its opponents by 9 goals would be about 4 games over .500.

The number of goals to get the extra win increases as teams get farther from .500...but usually that's not a huge problem in MLS.

[ChrisE]

Originally posted by beineke
Great work ... IMO, this is a very interesting result. Intuitively, I would've thought that fewer goals would buy you an extra win.

At some point, I'd like to go back to those save percentages and see how much of a difference a good shot-stopper might make.

Beineke, I compiled, I believe, teams' save percentages throughout MLS history. I tried doing a regression analysis, but seeing as it was the first time I'd ever tried anything remotely like that, I botched it pretty badly. If you feel like doing the work, I can give you the numbers.

(sorry to hijack your thread, JG)

[beineke]

From what I remember, after we adjusted for offsides, there was maybe a 10% gap from the best shotstopping defense to the worst (although most teams were nearly indistinguishable). If a team allows 5 shots on goal per game, the goalkeeping gap would be 15 goals over an entire season ... and 15 goals maps out to about 10 extra points.

Conclusion: Because the Burn finished 13 points behind LA, even Tim Howard couldn't have gotten them into the playoffs.