The Folly of Using 20-30 PAs to Determine Pitcher/Batter Match-Ups

by Jason Epstein

Citing Tigers manager Jim Leyland’s decision to bat Ramon Santiago second last night, Dave Cameron of FanGraphs explains why the choice was based on faulty reasoning, even though Santiago did collect two hits off of C. C. Sabathia:

What he found was that Ramon Santiago was 7 for 24 in his career against CC Sabathia, giving him a .292 average against the Yankees ace. How much that played into his decision to hit Santiago second, we can’t say for sure, but he did mention this fact to reporters before the game and he did hit Santiago second last night. It’s probably safe to assume that Santiago’s history against Sabathia played some role in his placement in the line-up. . . .

Batter/Pitcher match-up data has been shown to have no predictive value. In The Book, Tango/Lichtman/Dolphin devote an entire chapter — Ch 6, “Mano a Mano” — to looking for evidence that previous results of specific batter/pitcher match-ups would predict future results in those same match-ups. It wasn’t there. Despite looking at the 30 most extreme examples of matched-pairs where the batter had dominated the pitcher over a three year period, the group was barely better than average in the fourth season against those same pitchers. When looking at the flip side, where pitchers had dominated the hitters, the results were the same. Most interesting is that there was little difference in actual future performance by the 30 hitters who had dominated their rivals versus those who had been dominated by opposing pitchers. Even at the extremes, specific batter/pitcher data showed no real usefulness in projecting future results.

In reality, we shouldn’t be overly surprised that this data doesn’t really tell us anything. Even when looking at multiple years, you’re generally ending up with something in the 20-30 plate appearance realm, a ridiculously small number of confrontations from which to be drawing conclusions. But, the problems with batter/pitcher data go even deeper — in order to get a larger sample, you generally have to find players who have been matching-up against each other for many years.

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