Rule 3.03
A player, or players, may be substituted during a game at any time the ball is dead. A substitute player shall bat in the replaced player’s position in the team’s batting order. A player once removed from a game shall not re-enter that game. If a player who has been substituted for attempts to re-enter, or re-enters, the game in any capacity, the umpire-in chief shall direct the player’s manager to remove such player from the game immediately upon noticing the player’s presence or upon being informed of the player’s improper presence by another umpire or by either manager. If such direction to remove the substituted-for player occurs before play commences with the substituted-for player improperly in the game, then the substitute player may enter the game. If such direction to remove the substituted-for player occurs after play has commenced with the substituted-for player in the game, then the substitute player shall be deemed to have been removed from the game (in addition to the removal of the substituted-for player) and shall not enter the game. If a substitute enters the game in place of a player-manager, the manager may thereafter go to the coaching lines at his discretion. When two or more substitute players of the defensive team enter the game at the same time, the manager shall, immediately before they take their positions as fielders, designate to the umpire-in-chief such players’ positions in the team’s batting order and the umpire-in-chief shall so notify the official scorer. If this information is not immediately given to the umpire-in-chief, he shall have authority to designate the substitutes’ places in the batting order.
Rule 3.03 Comment: A pitcher may change to another position only once during the same inning; e.g. the pitcher will not be allowed to assume a position other than a pitcher more than once in the same inning.