What is BABIP, anyway?

I wanted to take a little bit more time to talk about BABIP. Batting Average on Balls In Play. I realize that I use it a lot in my posts, and I sometimes forget to go back over what exactly it means. Whenever a ball is hit into the field of play (foul or fair) and becomes either an out or a hit, then it counts as a ball in play. The percent of these instances that result in a hit is then known as BABIP. The statistic can be applied similarly to both hitters and pitchers. A hitter’s BABIP represents his own batting average on balls in play, while a pitcher’s BABIP refers to the batting average that he gives up to opposing hitters on all balls in play.

There are two important observations about BABIP. Firstly, a batter has a fair amount of control over his own average on balls in play. His ability to place the ball, go the opposite way, reduce pop-ups, hit line drives and leg out infield hits all contribute to the percent of balls he hits into play that end up being hits. Take two all-time-great Mariner lefties, Ichiro Suzuki and Ken Griffey, Jr. Their BABIPs – 0.356 and 0.289, respectively – are like night and day, a product of two distinct hitting styles. Ichiro is more of a slap hitter who finds holes in the infield while Griffey’s beautiful swing often sent balls out toward and over the wall in the King Dome. Despite his career BABIP being almost 70 points higher than Griffey’s, it would be tough to argue that Ichiro has been more valuable to the Mariner franchise. Thus, BABIP itself doesn’t tell us much about the offensive production of a player; rather it can only tell us exactly what its definition is: how often a player turns balls in the field of play into hits.

That being said, occasionally a player will go through streaks where the ball just can’t seem to find a hole, and conversely when the ball seems to have a mind of its own, slipping through every seam in the infield and clipping the foul lines. Because BABIP is a function both of a little luck, and a player’s own hitting traits, it is important to recognize when a player’s BABIP is reflecting skill or fortune. Ichiro has been better than great at finding holes during his career, but this season his BABIP figure is up to 0.384. Though he has finished two seasons in his career with a BABIP north of 0.384, at age 35 it is not likely that he can keep this pace, and his average is likely to fall about 10 points. This is the best way that BABIP is used, to predict future rises and falls in batting average.

The second important observation about BABIP is that pitchers can’t seem to control it (see this post for an explanation). Over the course of a career and even a season, a pitcher will face every type of batter, from the Ichiros to the Griffeys, and therefore his BABIP tends to take on the league average, about 0.300.

Predictions can be made in the same way with pitchers as with hitters. If a pitcher has a 0.350 BABIP halfway through the season, for instance, it is very likely that it will drop as the year goes on, reducing the number of runs that he gives up.

So, that’s BABIP in a nutshell! I hope it helps…

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2 Responses to What is BABIP, anyway?

  1. […] just under 4 runs per game while battling a brutal 0.363 BABIP (average on balls in play; see this post for more info). Though he just moved up from AA, all his key indicator stats have actually […]

  2. […] might be bad luck. Though Dave Cameron cautions against being too optimistic about Byrnes’ BABIP approaching anything near 0.300, a league-average rate, I see no reason that it won’t regress […]

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