Why you should understand BABIP

Whether you’re trying to win your fantasy league, or just trying to determine whether or not a player is going to bounce back from his slump, BABIP is statistic you should get to know. BABIP, or batting average on balls in play, represents the percentage of contacted balls that stay in the ballpark and actually become hits. The formula looks like this: (Hits – HR)/(AB – SO – HR + SF), and players’ BABIPs can be found at Baseball Reference so you don’t even have to put the work in!

The power of BABIP lies in the theory that hitters have a lot of control over their own BABIP statistic, while pitchers seem to have virtually no control over their own BABIPs. I will not go into why this is, because there is an excellent article about it here. Using this information, over time a pitcher can expect his BABIP to return to his team’s average BABIP, generally around 0.300, or 30%, while a hitter who has not begun his aging decline can expect his BABIP level out toward his own career average.

Take a guy like J.J. Putz. In 2007 he turned in a sterling stat card, posting a 1.38 ERA and 0.70 WHIP. However, his BABIP was a suspiciously low 0.200 on a Mariners staff that average 0.319. He has since come back to earth, as Mets fans are witnessing.

Conversely, if we examine rookie Nationals pitcher, Jordan Zimmermann, we see a different story. Based on his BABIP and peripheral pitching stats thus far in 2009, I believe Zimmermann will bounce back this season (barring injury). On the surface, his 5.71 ERA and 1.37 WHIP are not too attractive, but his 0.352 BABIP on a team that currently averages 0.310 can be seen more as bad luck than poor skill. His minor league strike-out rate has carried over to the show, and his walks are even down slightly. High strike-out rates prevent balls in play, which in turn prevent hits. If Zimmermann can continue to maintain his healthy walk and strike-out numbers, we can expect to see his BABIP fall, and with it his ERA and WHIP (for those of us fantasy nerds who care about that stuff).

BABIP is a simple way to help explain slumps and hot streaks, and help to predict a player’s future production. However, it is not an exact science, so be wary.


2 Responses to Why you should understand BABIP

  1. […] A few weeks ago I posted about BABIP, and it’s effect on a pitcher’s apparent ability. Pitchers are often the beneficiaries […]

  2. […] I have alluded before to the theory that pitchers have very little control over their BABIP statistic. In semi-plain English, the theory suggests that once a ball is hit into the field of play, the […]

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