Birnbaum: The Bayesian Cy Young

From SABR member Phil Birnbaum at Sabermetric Research on September 22, 2011:

At Fangraphs, Dave Cameron and Eric Seidman have a nice discussion (hat tip: Tango) on who’s the better Cy Young candidate: Clayton Kershaw, or Roy Halladay?

Part of the discussion hinges on BABIP: batting average on balls in play. As Voros McCracken discovered years ago, pitchers generally don’t differ much in what happens when a non-home-run ball is hit off them. Most of the overall differences between pitchers, then, are due to the fielders behind them, but mostly due to luck.

So far in 2011, Clayton Kershaw has a BABIP of .272, which Eric decribes as “absurdly low.” Still, Eric thinks it might actually be skill rather than luck, since since .272 it’s not that much different than Kershaw allowed in previous years. Dave argues that Kershaw’s three seasons is still a fairly small sample size, and points out that most of his BABIP advantage comes from his record at home (he’s about average on the road).

Anyway, my point isn’t to weigh in to which one is right — they do a fine job hashing things out in their discussion. What I want to talk about is something they both seem to agree on: that it’s important whether the BABIP is luck or skill. If it’s luck, that reduces Kershaw’s Cy Young credentials. If it’s skill, he’s a better candidate.

Seems reasonable, and I don’t necessarily disagree. But let’s see where that logic leads.

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Originally published: September 22, 2011. Last Updated: September 22, 2011.