George Brett
Kansas City Royals
Sept. 19, 1980: .400
Hitting .337 at the All-Star break, Brett got hot in July (.495) and kept it up in August (.430) despite torn ligaments in his ankle. He spent 15 days above .400 in August and climbed back to the magic mark (.3995, to be precise) on Sept. 19. Brett went 14-for-46 over his final 13 games, finishing at .390.