THE BOOK--Playing The Percentages In Baseball

There are several unexplained factors that could skew the reults of this study.  In addition to the IBBs that Tango mentioned, a batter may bat eighth if he has a platoon disadvantage against the opposing pitcher and be moved up in the lineup if he has a platoon advantage so handedness needs to be considered.  Also, the pitcher batting ninth is usually replaced by a non-pitcher in the lineup at the end of the game when the the better relief pitchers are pitching so the quality of the opposing pitcher should be controlled for.

The controls Peter suggests would be good, but I doubt they would change the conclusion.  The first factor would mean that Jeff’s estimate actually understates the benefit of hitting in front of the pitcher.  And the second factor is probably minimal:  relief pitchers in the aggregate post about the same ERA as starters, plus some of the non-pitcher PAs come in games the batter is not hitting 8th (and so are not limited to late innings).

What I thought was interesting about Jeff’s results is what it means for studies of protection, like Drinen/Bradbury’s.  The impact of the pitcher on NL #8 hitters will create the illusion of “anti-protection”—the better the hitter is behind you, the worse you hit.  However, the pitcher impact is a special case, and likely tells us nothing about whether a Cardinal hitter will do better hitting in front of Pujols or Ankiel (if it matters at all).  So I think anyone studying the protection issue needs to omit 8th place NL hitters.