The Baseball Exchange

A Comment on BABIP by 27yankees

I’d just like to make a comment on BABIP. BABIP, or batting average on balls in play, is a measure that was discovered a few years ago by a writer on Baseball Prospectus. He discovered with a bit of research that BABIP varies a lot for all pitchers, great ones, or not so great ones. The difference he discovered between the great pitchers and the not-as-great pitchers was that the great ones struck out more batters, walked less batters, and gave up less home runs. Good pitchers are able to compensate for a high BABIP, or some bad luck, by striking out more batters, walking less batters, and giving up less homers. That’s what made Pedro Martinez so good. In addition to coining the term BABIP, he coined the term “peripheral stats”, which are stats like K/9, BB/9, and HR/9, which indicate how well a pitcher should be able to compensate for BABIP. This lead to the creation of peripheral ERA, or ERAp. This was a stat that indicated how well we should have expected a pitcher to perform given an average BABIP.

However, since that study was conducted in 2001, a few holes have been discovered. For one thing, there are pitchers out there who are able to maintain consistently at consistently low BABIP – typically extreme sinkerballers – Chien-Ming Wang, Brandon Webb, and Fausto Carmona were good examples of pitchers who had better numbers than their peripheral stats indicated.

However, what I really want to address is a very common misconception. Even my fellow writer Red used this misconception in the previous post, to some extent. The misconception is that BABIP is as random for hitters as it is for pitchers. Among pitchers, there are pitchers who consistently put up a trend of having low BABIP’s or high BABIP’s, but for the most part, BABIP comes from how good the fielders of the team are and from luck. With hitters, however, this is just not so. For hitters, there is a clear trend showing that BABIP is a skill. Some hitters, like Ichiro!, and Derek Jeter, quite consistently post very high BABIP’s. Some hitters, like Jack Cust or Pedro Feliz, consistently post low BABIP’s. That’s not to say that there isn’t luck involved in hitter BABIP, too. Just take Jorge Posada, who had a .389 BABIP in ’07. For a hitter, he posts a typically high BABIP, around .320, but it is quite clear that quite a bit of luck was involved in his season.

But for the most part, hitters maintain the similar BABIP’s year in and year out, with a bit of decline as the player gets older and slower, and just a touch of luck in the mix. Though BABIP is variable just as much as any stat, if you compare the standard deviation of a hitter’s BABIP to that of a pitcher, it is obvious that the pitcher’s BABIP is much more reliant on luck.

Hopefully that helps to clear up that misconception a bit.



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