PITCHER CHANGING DEFENSIVE POSITIONS
Rules 5.10(d) Comment, 5.10(g):
The purpose of this Comment is to prohibit a player from being a substitute for a pitcher more than once in the same inning. Thus, a player who starts (or enters the game during) an inning as a pitcher may substitute for any position(s) afterwards; however, he may not return to the pitching position more than once in the same inning. Similarly, a player who plays a position(s) other than pitcher in an inning may substitute for a pitcher once, and then play any position other than pitcher afterwards in the same inning—in this case, the fielder would not be allowed to return as the pitcher for the remainder of that inning. Finally, keep in mind that Official Baseball Rule 5.10(g) applies to such pitching changes, such that if the pitcher is replaced, the substitute pitcher must pitch to the batter then at bat until an out is recorded, the batter reaches base safely or the side is retired, unless the substitute pitcher incurs an incapacitating injury. Any pitcher entering the game regardless of whether he is entering the game for the first time or retaking the mound from another position is permitted to throw warm-up pitches in accordance with the Pace of Game Procedures.