Fun with Small Sample Sizes: Catchers’ ERA

Last night, while Twittering about the game, Ross from New Stadium Insider posed the following question:

Can someone get the following stat for me: Yankee pitcher’s ERA with Posada behind the plate (and # of innings) vs. when Molina catches?

Always up for a run through Baseball Reference, I obliged. The findings were not pretty. Counting last night’s game, Jorge Posada has caught 105 innings, and Yankee pitchers have a 7.97 ERA in those innings.

There is one caveat though. Posada has caught all six of Chien-Ming Wang’s innings. Since Wang has been epically bad, it’s not fair to Jorge to saddle him with those runs. So Jorge has caught 99 non-Wang innings and has seen his pitchers surrendered 70 runs. That’s an ERA of 6.36.

On the other side of the ball is Jose Molina. The Yanks’ defensive specialist has caught 58.1 innings this year, and pitchers are throwing to the tune of a 3.09 ERA. That’s a rather stark difference.

Now, these numbers suffer from an obvious sample size problem. Jorge’s 100 innings are far to small a sample to judge his catching, and Jose’s numbers in fewer innings are equally as suspect.

Right now, though, with the Yanks’ pitchers going as they’ve been going, it’s hard not to notice the difference. Pitching to Jorge Posada, the Yanks’ staff has been absolutely horrible; pitching to Jose Molina, the Yanks have among the best ERA in baseball.

What this means right now for the Yankees is nothing. The Yanks need Jorge’s bat in the line up, but they also need him to draw some semblance of success out of his pitchers. For now, is too early to draw any conclusions, but this is certainly a trend worth watching.