BACKSWING (FOLLOW-THROUGH) HITS CATCHER

Rules 6.03(a)(3), 6.03(a)(4), 6.03(a)(3) and (4) Comments:

If a batter strikes at a ball and misses and in the umpire’s judgment unintentionally hits the catcher or the ball in back of the batter on the follow-through or backswing while the batter is still in the batter’s box, it shall be called a strike only (no interference). The ball will be dead, however, and no runner shall advance on the play. If this infraction should occur in a situation where the catcher’s initial throw directly retires a runner despite the infraction, the play stands the same as if no violation had occurred. If this infraction should occur in a situation where the batter would normally become a runner because of a third strike not caught, the ball shall be dead and the batter declared out regardless of the location of the baseball at the time the backswing hits the catcher.
This interpretation applies even if the catcher is in the act of making a throw to retire a runner. That is, if the batter is in the batter’s box and his normal backswing or follow-through unintentionally strikes the catcher or the ball while the catcher is in the act of throwing, “Time” is called and runners return (unless the catcher’s initial throw retires the runner).