When one has tickets to an NBA, NHL, or MLB playoffs, but the game they had tickets to becomes cancelled, as one team had already won the series. Only used for Game 5's, Game 6's, or Game 7's, the games that are scheduled as "if necessary," the derivation of the phrase.
Mike: "Hey, how was the Red Sox- Angels game last night?"
John: "The game was if necessaried; the Angels already swept."