The Month Pinch-Hitting Got Easier by Neil Weinberg May 4, 2016 Baseball’s brilliant chaos attracts fans of all sorts of analytical dispositions. Some people like to go with their gut, some trust their radar gun, and others prefer to dive into the spreadsheets. No matter with which group you align most closely, it’s very likely you agree with the following: pinch-hitting is super hard. The precise difficultly is a matter of some debate, but everyone is pretty much on board with the concept. Batters perform worse coming off the bench than they do when they are already in the game. This was one of the notable findings in The Book and plenty of research has picked up on it from there. But, uh, here’s a weird thing: Pinch-hitters are performing substantially better in 2016 than they have in recent seasons. In fact, if this early season trend holds, this will be the best pinch-hitting season for which FanGraphs has positional splits. In cases like this, the safe assumption is that we’re observing a strange blip and things will get back to normal before too long. After all, it seems like teams are favoring relievers over bench players these days, so this finding appears particularly out of step with our expectations about the direction in which the game is headed. If anything, the pinch-hitter penalty ought to increase as the game drifts toward bullpens full of 95 mph fastballs and benches populated exclusively by Romine brothers. But this season’s pinch-hitters have my attention and I think it’s worth looking for an explanation, even if we’re skeptical about how meaningful one month of data is. Is It April? This time of year, the easiest culprit is the month of April. For a variety of reasons, the season’s first month sometimes plays tricks on us. Sample size, weather, and a lack of fatigue/injuries can all lead to some atypical results if you look at them in isolation. To test this, I grabbed pinch-hitting data from each of the previous six Aprils. On average, pinch-hitters actually perform slightly worse in April than during the season overall. While this isn’t definitive, history suggests full season number will go up rather than down. At most, you might expect to see a 4% decrease in PH wOBA when comparing April to the full season, but it’s more common to see a small increase (larger than the average league wOBA increase from April to the full season, even). Granted, if pinch-hitter wOBA dropped by 5% from April to the full season this year, we’d be about in line with our typical pattern, but that would require you to bet on the largest negative in the sample instead of the average. It’s not a satisfying explanation to say that it’s just April. It might be, but the evidence doesn’t support that idea very strongly. Is It the Hitters? Another possible explanation is that the sample of pinch-hitters is better this year than in year’s past. This doesn’t hold water, either. I created an expected wOBA for the group of April pinch-hitters using their preseason Steamer projections weighted by their actual PH PA for April 2014-2016 and compared it to the overall league wOBA for that April and full season. If anything, the group of pinch-hitters is worse relative to the league this April and no better than the league over a full year. Projected wOBA for Pinch Hitters vs League Year Projected wOBA for April PH Full Season MLB wOBA April MLB wOBA 2014 0.312 0.310 0.313 2015 0.300 0.313 0.307 2016 0.304 0.316 0.316 Presumably, you could argue that this group of pinch-hitters is unusually good at pinch-hitting specifically, but there hasn’t been a lot of previous research to suggest pinch-hitting is much of a skill. And if it were, it seems like it probably wouldn’t show up out of nowhere like this with the entire league suddenly figuring out which hitters are good at avoiding the PH penalty. In case you’re wondering, it’s not a platoon thing. Over the last three Aprils the percentage of PH PA where the batter had the platoon advantage is 69%, 70%, and 69%. What About Situations and Approach? It’s also possible that pinch-hitters are being used differently and are entering games in situations more conductive to hitting than in previous years. That, too, isn’t the case. The average leverage index for April PH PA is essentially identical and the average inning in which pinch-hitters are used is unchanged. Pinch-hitters are even seeing the same number of pitches, averaging an end to their PA on a 1-1 count in 2016 and 2015. It’s not a perfect comparison, but this would seem to indicate the results aren’t a product of a more or less aggressive set of pinch-hitters. And keep in mind, we’re talking about pinch-hitters improving relative to the rest of the league. So while there are plenty of theories about MLB switching to a new baseball to jump start offense last summer, there’s no reason why that would have a disproportionate effect on pinch-hitters. I could definitely imagine ways in which the pinch-hitter penalty could decrease. With new technology, better scouting reports, and better indoor training facilities, it seems plausible that teams could figure out a way for hitters to feel like they’re in the game even when they aren’t. But there’s no reasonable explanation for why something like that would take hold all of a sudden. It’s important to remember that unusual things happen and that sometimes there’s no direct cause, but given how predictable the PH penalty has been, this is something I will be watching very closely over the next few months. Pinch-hitters are hitting much better this year. It’s not just an April thing. It’s not because teams are using better pinch-hitters. And it’s not because they’re being deployed in an obviously new way. There may be a cause we’ve yet to determine or it may just be an unusual series of events. At the very least, this is something worth monitoring as the season unfolds.