LINEUPS AND SUSPENDED GAMES
Rule 7.02(c):
The Comment to Official Baseball Rule 7.02(c) states that if immediately prior to a game becoming suspended, a substitute pitcher has been put into the game but has not retired the side or pitched until the batter has been put out or has become a base runner, when the game is resumed such a pitcher may, but is not required to, start the resumed portion of the game. If such pitcher does not start when the game is resumed, he will be considered as having been substituted for and may not be used in that game.
If a game is suspended during a manager’s or coach’s trip to the mound (or after the trip but while the same batter is still at bat), a new pitcher may be substituted when the game is resumed.
If a pitcher has been brought into the game but has not faced one batter (or retired the side) when the game is stopped for weather, such pitcher may, but is not required to, continue pitching when the game is resumed.