可以隨時替換受傷球員,只能用相同位置去換相同位置,例如投手換投手,野手換野手,但被替換的,下一輪不能上場
記得之前有人說不用相同位置,但我查了一下,這規定還是有,有誤請指正

A rule change this year allows a team to replace an injured player while a playoff series is ongoing. Pitchers must replace pitchers, and position players must replace position players. An injured player removed in the middle of a series cannot be included on the roster of the subsequent series