BABIP: Skill Meets Luck
You've heard about BABIP. What is it and how do you understand it?
Baseball is not immune to the phenomena of acronyms and in fact it might be one of the worst offenders in the entire universe: OPS, HR/F, LOB%, PECTOA, WAR… the list goes on and on. In what follows I will be talking about BABIP which stands for Batting Average on Balls in Play. You've heard of it no doubt, but do you really understand it? I'll try and explain a little bit about it before digging into the guts of it and looking at 2014 performances.
WHAT IS BABIP?
BABIP, also referred to as a player's hit rate, is the rate at which batted balls end up as base hits. There is one caveat with BABIP – it removes home runs from the equation because technically the ball isn't in play on a home run (it never lands in the field of play). Here is the simple formula in play for the measure we call BABIP.
A few points to consider when it comes to BABIP.
(1) The major league average for BABIP is traditionally in the .290-300 range. Last season the Cubs had the worst mark in baseball at .275 while the Red Sox had the highest at .329. Seventeen of the 30 teams finished between .290 and .305.
(2) Players tend to establish their own level of BABIP production over the years. That means if a guy has produced a .275 mark for three seasons and then he suddenly produces a .325 mark, chances are better than even that his BABIP number will regress in the coming season. However, if a player produced a .325 mark year after year and slumps to .275 one year that doesn't always mean he will remain at that lower mark moving forward. Whether good or bad, players tend to establish a fairly consistent pattern over the course of multiple seasons (a rolling three season timeframe gives a very solid gauge as to what expectations are for the current/coming campaign).
(3) A player who is performing at a rate that is below his established level can be said to be hitting in "bad" luck. That's too simplistic of course, but it's a down and dirty way to look at it. Therefore he is likely, if you believe in the percentages, to see his batting average increase (this is especially true if his line drive rate is artificially low. The same can be said if his line drive rate is high and the hits still aren't falling).
(4) A player who is performing at a rate that is above his established level can be said to be hitting in "good" luck. This is also far too simplistic but it suits the purpose of this piece as I try to explain how to read BABIP. Therefore he is likely, if you believe in the percentages, to see his batting average decrease if his BABIP is significantly higher than “normal.” Remember, players set their own baselines.
(5) An all or nothing slugger like Chris Carter has a large portion of his at-bats result in a home run, a walk or a strikeout (Carter had 29 home runs, 70 walks and 212 Ks last season). He had a rather amazing total of 311 of his 506 plate appearances end in one of those three events meaning that 61 percent of his at-bats ended in a home run, walk or strikeout. Therefore, his BABIP mark could show some fluctuations since it is directed to a rather paltry sum of at-bats. His batting average therefore is always in danger of floating up and down (Last season his BABIP was .311 and he hit .223. This season his BABIP is only .214 and he's batting .168). At the other end of the spectrum there are swing at everything/contact type hitters like Norichika Aoki. In his 674 plate appearances last season he hit eight home runs with, 55 BB and 40 K. Therefore only 103 of his plate appearances ended in one of those three events meaning that his percentage of three outcome occurrences was only 15 percent. Guys like Aoki have more of a stable base to work with the thinking being that 500 plate appearances gives a guy a big enough sample size that things will stabilize versus being randomly effected by a couple of batted balls finding a guys glove when they may not have last year. Regardless remember that players tend to establish their own baselines.
(6) BABIP isn’t just a useful tool to gauge hitters. Obviously if the major league average is in the .290-300 range then it is easily identifiable when a pitcher is hurling in “good” or “bad luck” as well (again too simplistic but it suffices for what we're trying to accomplish here). As we all know, pitcher’s tend to vary from season to season a bit more than hitters, but the same theory still basically applies to hurlers: pitchers tend to establish a baseline for the BABIP mark, though a bit more variance than that posted by hitters can be expected. Still, if a pitchers owns a career BABIP mark of .305 and then one year posts a .240 mark, chances are pretty good that number will regress in the coming year, and with that regression the overall work of that particular hurler will likely also dip a bit.
In my next column I'll dig in to the 2014 numbers and point out some players with odd BABIP's.