If they add the Negro Leagues to the record book, then I believe Josh Gibson becomes the most recent player to bat .400 for a full season (1943) if he had enough at-bats. But the statistics I can find online underscore the problem: Seems like different sites give different numbers for him that year. From what I understand, that’s always been the difficulty with Negro League statistics—they simply weren’t maintained as reliably as MLB statistics were and they can’t always be reconstructed properly.
even if you sort the differences (some include post season and the all star game in the quotes), one issue with rate stats is the season were pretty short in terms of league ball. 70 or so games. There have been guys to hit .400 for that short of a period. I think Gwynn did it, and maybe Olerud and Brett.
