Myth Busting

I have read something to the effect that minor league pitchers who allow a very high batting average on balls in play should raise a big red warning sign. The theory is something like this: Unlike a high BABIP from an established major leaguer, which you might assume to be a product of bad luck, it means the pitcher does not have the stuff to translate into the big leagues. So even if he has a good strikeout rate, he will suffer a worse translation to his peripherals (HR, BB, SO) than a tough to hit prospect pitcher.

I don't remember who said this first, where I heard it, or if anything was published on it or not, but I thought I'd check it out.

I looked at all AAA pitchers in the last 5 years who also pitched in the Major Leagues, using the matched innings method. The minor league pitching stats were regressed to the league average. My sample size is pretty good here, 31,945 innings. The AAA to majors factors for 2002 to 2006 have been:

BB 1.28
SO 0.83
HR 1.40
BABIP 1.01

The ratios are walks/batter faced, strikeouts/batters faced - walks, and HR/fair contact (BFP-K-BB).

Now, I look at only those pitchers who had a high (.325 or above) BABIP. My sample size is 7803 matched innings. My translation rates are:

BB 1.24
SO 0.80
HR 1.35
BABIP 0.942

Not a lot different. The peripherals are all close enough that we can assume its just sampling error. The hittable pitchers do a little worse in strikeouts than pitchers overall, but actually do better in walks and homers. The BABIP is actually lower in the majors, since we have selectively sampled pitchers with high minor league BABIP. I think its safe to say that they were a bit hit-unlucky in the minors.

In conclusion, its a myth that a high BABIP in the minors dooms a prospect. Its always good to not allow hits (duh, that's why no-hitters are so cool), but if you've got two prospects, and both are equally excellent in walks, homers, and strikeouts, and one has a higher BABIP, take the one who gives up fewer hits. But don't give up on the other guy so quick. He can probably pitch too.

This is not what I expected. I thought there might be an effect, and was looking to measure the effect, redo the CHONEs, and knock Jason Windsor down a peg. He's a classic high hit, good peripherals pitcher in the Oakland system. But there's nothing here. His numbers are every bit as likely to translate into decent major league pitching as most good AAA pitchers. Oakland isn't going to fall apart without Zito. Angels are going to have to step it up a notch to reclaim the west.