I am a skeptic on the benefits of pinch hitting. I don’t think that it is always a poor decision, but I do think that too often an incomplete accounting of the factors involved are considered and managers, everyone’s favorite scapegoat, are disproportionately blamed or praised, largely on a results-based basis. Pinch hitting is difficult. Hitting is difficult enough, but the first trip up to the plate is even harder on the hitter. Additionally, the decision usually has more consequences than just this hitter or that one for this one plate appearance. Detailed analyses of pinch hitting is not new, but when left-handed Michael Saunders hit against left-handed Brian Fuentes this morning in the top of the tenth inning while right-handed Casper Wells sat on the bench, I decided to do my own digging.
The straight forward stuff like determining a difference in hitter’s skill and factoring in the potential — the opposing manager could always reciprocate with a pitching change after all –- platoon advantage and pinch hitter penalty can be gleaned from Klaassen’s article linked above. My own determination after those three aspects were evaluated was that Casper Wells was approximately a 50 point (wOBA) better hitter than we should expect Michael Saunders to be. That difference translates to about 0.04 expected runs, a rather paltry looking number even for such a sizable gap in expected performance. The reality is that a single hitter, in a single plate appearance, is just not very likely to swing things much through skill alone. Chance plays a huge rule in individual outcomes in baseball.
That’s all standard fare, but there are two aspects that I’ve found usually missing in pinch hitting discussions that I wanted to spotlight. The first is leverage. Much of pinch hitting occurs in higher than average leveraged situations and that should be accounted for. Even though there were already two outs and nobody on the bases when Saunders stepped in against Fuentes the leverage of the at bat was 24% greater than normal due to the game being tied in extra innings. In fact, at bats taking place after the 8th inning — when a lot of pinch hitting takes place — show an unsurprising rise in leverage, averaging around 1.35.
This at bat wasn’t just in extra innings though. It was in the top half of extra innings, which means that regardless of the plate appearance, the Mariners would have to play defense for at least one more inning. Both Saunders and Wells have too small samples to make a strong objective distinction between the two, but I believe the subjective consensus is that Saunders is the stronger fielder. The gap in defensive value that favors Saunders is smaller (probably something like 10% as big) than the gap in hitting value that favors Wells, but it does exist and mounts with each additional inning played while plate appearances only come around about every other inning.
Furthermore, there are alternative uses for Casper Wells that might return a greater value. Manager Eric Wedge employed one such use in the following inning after the Mariners grabbed the lead when he replaced Mike Carp in left field with Wells, a defensive upgrade of far greater magnitude than Wells versus Saunders. Had Wedge used Wells to pinch hit for Saunders, the only remaining player available who had outfield experience was Chone Figgins, already in the game at third base, and years removed from regular duty in the outfield.
A move could have been made, Wedge had several bench players capable of handling third base, but it’s far from clear that it would be a net gain in defense unlike the swap of Wells for Carp which was probably about a 20-run change over a full season. That’s still a very small amount of gain and, according to my numbers, still less than would have been gleaned from pinch hitting earlier. So in this case, pinch hitting does look like the better move albeit one that offered little expected gain. Just don’t forget to think about leverage and defense along with the talent of the hitters when you’re contemplating potential substitutions.
Matthew Carruth is a software engineer who has been fascinated with baseball statistics since age five. When not dissecting baseball, he is watching hockey or playing soccer.