A quick look at momentum
In the comments of an earlier post, it was brought up (I forget by who) that momentum going into the playoffs - specifically, a winning record in September - translated into winning in the playoffs. So I decided to test this.
Fair warning: this is not a detailed study. This is the simplified study that it took me 30 minutes to do. I took a quick look at playoff series from 1995 to 2007, essentially the Wild Card era.
First, let's look at the correlation. The correlation between a team's win-loss record has a .38 correlation with their postseason win-loss record. So, not terribly strong, but certainly notable. A correlation between a team's W-L record in September and their W-L record in the postseason? -0.02. In other words, basically meaningless.
Now, to the head to head record. The team with the best regular season W-L record won each series 61% of the time. The team with the best September W-L record won each series 39% of the time.
Just so's I'm clear, here is what I am saying:
- Momentum is not a very good predictor of playoff success.
- The best teams in the regular season tend to be the teams to win in the playoffs.
I am not claiming that there is no benefit whatsoever from momentum; that study would require more detail than what I am showing here. But if there is an effect from momentum, it is probably a very tiny effect, sort of like the difference between letting Jason Marquis hit and letting Casey McGehee hit (who is now the Brewers' problem, by the way). Certainly it's better to win ballgames in September than to lose them - hell, I advocate winning all 162 of them if at all possible. I am 100% behind the idea of winning as many ballgames as is humanly possible.
But I don't think there's any reason to think that momentum is the reason the Cubs lost in the playoffs this year, or that getting momentum next season would greatly improve the Cubs' chances.