Alex Rodriguez and the Predictability of October

Alex Rodriguez entered the Yankees ALDS against the Twins with a playoff wOBA of .377 in 170 plate appearances. Certainly an impressive mark, given a league wOBA ranging from .330 to .340 in the years in which Rodriguez’s teams reached the playoffs. However, his playoff stats pale in comparison to his regular season performance, where he performed as one of the top hitters in the game, with a wOBA of .412. This 35 point difference works out to roughly an 18 run difference over 600 plate appearances. This large difference in regular season and playoff performance has led to the media blasting Rodriguez with such names as “Mr. April.”

Is it really fair, though? We in the sabermetric community certainly understand the dangers of judging a player on 170 plate appearances. Players slump. Players play while injured. Many things can happen to produce 170 plate appearances below a player’s natural ability. BABIP luck can come into play with samples of a full season, and even more so with the sample size of less than a third of a season we have with Rodriguez. Due to the small sample size, his wOBA is actually within one standard deviation of what we’d expect based on his career numbers.

That’s even without considering that the pitching staffs of playoff teams have allowed a .301 OBP over the last decade, for an OBP+ allowed of 89. Similar results occur with other statistics. Simply put, we should not expect hitters to fare as well against the superior pitching staffs they encounter in October. What makes Derek Jeter so remarkable isn’t that he performs so much better in the post-season. His wOBA in the playoffs is only 2 points higher than his career norm – .377 vs. .375. What is remarkable is that he’s done it consistently (a significant sample of 576 PAs) against superior run prevention.

As Rodriguez showed in the series against the Twins, it just plain doesn’t work to make the kind of assumptions that Rodriguez’s reputation as “unclutch” would have many making regarding his playoff hitting ability. So let’s take a quick look at his numbers before and after this year’s ALDS.

Note: I am not including SB/CS numbers in wOBA calculation

Regular Season: 9611 PA, .390/.576/.965, .405 wOBA, .362 BABIP

Postseason (Pre-2009): 170 PA, .376/.483/.859, .372 wOBA, .333 BABIP

Postseason (Current): 182 PA, .381/.519/.900, .388 wOBA, .355 BABIP

It only required 12 ridiculous plate appearances to boost Rodriguez’s playoff wOBA by 16 points. Over 600 plate appearances, this would be an 8 run swing, or nearly a win. Not only that, his postseason numbers approach his career numbers, and are a statistically insignificant distance away (roughly .4 SDs). Again, this is even without adjusting for the quality of run prevention he’s facing.

Next time you hear somebody telling you about how unclutch Rodriguez, or for that matter, any other player, is in the playoffs, there are things we must keep in mind. First, wOBA and all other offensive stats are extremely volatile over the small sample sizes we have with the playoffs. We see this even with teams like the Yankees that reach the postseason on an almost yearly basis, due to BABIP fluctuations and other factors. Second, it’s not reasonable to expect (or demand, in the case of some fans) a superhuman increase in production in the postseason, due to the increase in the pitching and defensive talent they will face.