 Since most professional baseball games are nine innings long, the fifth inning is used as the threshold for an official game.If the visiting team is leading, or the game is tied, the end of the fifth inning marks this point.If the home team (which bats last) is already ahead in the score, and theoretically would not need its half of the fifth inning, then 4½ innings (i.e., the middle of the fifth) is considered an official game.