Conventional wisdom says that left handed batters hit better against right-handed pitchers (and vice versa), but, on rare occasions, the stats don’t appear to back that theory up.
Brennan Boesch appears, on the surface, to be one of those curious cases. He now has over 800 major league plate appearances (634 versus right-handed pitching and 201 versus left-handed pitching), and his batting line exhibits a “reverse platoon split.” So far in his young career, his batting average, on-base percentage, and slugging average are all higher when facing same-handed (left) pitching (.347/.408/.523 to .254/.315/.422)*.
The causes some Tigers fans to bemoan Jim Leyland’s tendency to bench Boesch in favor of right-handed hitters such as Casper Wells when a lefty is on the mound.
But I think this is a case where the stats are lying to us. At least, they are if we’re using them in a predictive sense. When we dig deeper into the numbers, we see that the difference in his lefty-righty splits can be completely contributed to luck on balls in play.
For his major league career, Boesch’s batting average on balls in play (BABIP) stands at .422 versus lefties, but only .279 versus righties. It’s possible that his “true” BABIP skill is higher versus lefties than it is versus righties, but not by this much. Not even close.
Brennan’s career minor league splits followed the traditional trends. His OPS versus righties was .759, and against lefties it was .632. Even in his last couple of years in the minor leagues when he saw a jump in his power to become more like the hitter he is today, he still exhibited the “normal” platoon splits. And when we look at Brennan’s minor league BABIP numbers, we find he never displayed this type of extreme reverse-BABIP split for a full season. His most extreme example of a reverse-BABIP platoon split was in AA Erie when his BABIP was .327 against left-handers and .301 versus right-handers (he was .305 versus lefties and .317 versus righties for his minor league career).
So what does all of this mumbo-jumbo mean? It means that we should expect him to start hitting a little bit better versus righties, and a little bit worse versus lefties.
If we regress his BABIP splits to more reasonable numbers (say .300 versus right-handed pitchers and .325 versus left handed pitchers) we find that the difference in his batting line completely goes away. Actually it more than goes away; we would see his OPS versus righties climb to .769 and versus lefties fall to .751. And this is still assuming that his true BABIP skill is better versus left handed pitchers (which probably actually isn’t the case).
If we assumed his BABIP skill was the same versus either handed pitcher (say around .325), his OPS platoon split would figure to be around .810/.750 (in the traditional manner).
There’s not nearly enough statistical evidence to suggest that Boesch actually carries a reverse-platoon hitting skill. So instead of criticizing Leyland for not playing “the statistics”, we should applaud him for looking past the superficial evidence.
*All stats are entering play on Sunday