BP: Baseball's make-or-break month

March, 29, 2010
3/29/10
11:20
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By now, you've heard your favorite team's manager say something like "We're hoping to get off to a good start this year, because that's the key to a good season." All managers say some form of this cliché during spring training, and it's hard to argue with. After all, it's not like losing a bunch of games in April is good for a team's chances at playing in October. Last season, the Dodgers ended the month of April at 15-8 and made the playoffs. The Mets went 9-12 and didn't. Clearly, a team that jumps out to a good start has an advantage, right? But is success in April more important than in any other month?

To figure this out, I took all teams since the beginning of the wild-card era and found their record in each month of the year, plus their end of the season record to figure out the correlation between their April record and their end-of-season record. In a correlation, 0 means there's no relationship, while 1.0 means that one perfectly predicts the other. April has a correlation of .553. Not bad, not great.

What about the other months? Well, it turns out that they all have stronger correlations with the seasonal record than April. A team's record in May has a correlation of .617 with seasonal record. June has a correlation of .562, and July has a .579. But the two months that are the best indicators of seasonal record are August (correlation of .673) and September (.666). Yes, April record has the lowest correlation with final record. And when I isolated playoff teams, the results were pretty much the same. August and September again had the highest correlation, followed by July, May, April and June.

So, if you really want to know what a team is made of, your best bet is to look at what they do at the end of the season, not the beginning. It's not that April is a horrible predictor of eventual success or failure, but its predictive power is moderate at best and the other months are better bellwethers. If your team doesn't get off to a good start in April, don't worry too much. There's time left in the season.

Russell Carleton is an author of Baseball Prospectus.

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