In “The Book”, Tom Tango, Mitchel G. Lichtman and Andrew E. Dolphin estimated that hitters coming off the bench to pinch-hit do not perform up to their expected levels. They calculated a .034 average drop in wOBA for hitters from their season norms when pinch-hitting, and found no evidence of pinch-hitting specialists who were even as good as in their other plate appearances.
If this is part of the nature of the game, such as the platoon differential, then it should manifest itself in Nippon Professional Baseball as well. While the evidence suggests pinch-hitters do lose something coming off the bench in Japan, the drop in performance does not appear to be anywhere near as severe as the effects Tango, Lichtman and Dolphin observed in their major league data.
NPB as a whole
Because I don’t have the tools to compute wOBA for players in Japan prior to 2017, I’m opting for the poor-man’s substitute, OPS2, calculated as: on-base percentage x 2 + slugging average ) / 3.
This allows me to look at all seasons for which we have results for each plate appearance. My current data set has every regular season plate appearance in NPB from 2002 to 2019.
For simplicity’s sake we’ll omit the current season and look at 2002 to 2018. During this stretch, 47,499 players were announced as pinch-hitters and 46,848 of those actually completed a plate appearance.
Those batters had an average OPS2 of .313 in all their plate appearances in seasons, and a .308 OPS2 as pinch-hitters, a drop in expected performance of about 1.8 percent.
During the 18-year span from 2002 to 2018, eight players had 300 or more pinch-hit plate appearances, discounting sacrifice bunts, which don’t count for anything in OPS2.
Two of the eight were somewhat better as pinch-hitters during the period of the study, and one, Kenji Yano, was significantly better. In 390 pinch-hitting appearances in which he didn’t successfully sacrifice, he posted an OPS2 of .363. In all other PAs, his OPS2s during the study was .342.
Five batters were worse as pinch-hitters to the tune of .001 to .010, while one batter, Shinjiro Hiyama was far worse. Hiyama had 607 pinch-hit appearances, the most in the study. During those seasons in which he appeared as a pinch-hitter, Hiyama posted a .360 OPS2 as a regular, .315 as a pinch-hitter.
So this doesn’t refute the claim that there is a cost to pinch-hitting, it does open the door for the possibility that some batters in some circumstances have an affinity for it – which Tango, Lichtman and Dolphin rejected.
As for how different NPB managers have fared in their use of pinch-hitters for position players, that info is HERE (paid content alert).