A one-game playoff, sometimes known as a pennant playoff, tiebreaker game or knockout game, is a tiebreaker in certain sports—usually but not always professional—to determine which of two teams, tied in the final standings, will qualify for a post-season tournament. Such a playoff is either a single game or a short series of games (such as best-2-of-3).
This is distinguished from the more general usage of the term "playoff", which refers to the post-season tournament itself.
Major League Baseball
One-game playoffs were used in Major League Baseball (MLB) through the 2021 season. When two or more MLB teams were tied for a division championship or the wild card playoff berth (1995–2011, or starting in 2012, the second only) at the end of the regular season, a one-game playoff was used to determine the winner.
If a tie were (from 1995 to 2011) a two-way tie for a division championship and both tied teams' have records higher than those records of the second-place teams in the other divisions, or (from 2012) between the two division non-champions with the untied best record, no one-game playoff was played. In this scenario, the winner of the season series between the two teams wins the tiebreaker for purposes of playoff seeding. Through the 2008 season, home-field advantage for one-game playoffs was determined by a coin flip, but effective from , home advantage was based on a set of performance criteria, with the first tiebreaker being head-to-head record.
For statistical purposes, one-game playoffs were considered part of the regular season. In a 162-game regular season, a one-game playoff was often referred to as “game 163”. The result of the playoff was included in the regular season standings and individual player statistics were included along with the statistics for the rest of the season. One significant playoff-like deviation from normal regular season games in force was that six-man umpire crews were used (as opposed to the four-man crews of the regular season). Also, television broadcasting rights for all were negotiated by MLB – from 2012 to 2021, the network owning the rights to the Wild Card Game for a particular league has also had the rights to any tiebreaker(s) that might occur in that league.
MLB scheduling practices stipulated a break of at least one day between the scheduled end of the regular season and the start of the postseason. The schedule was designed to maximize the probability that tiebreakers could take place on the day after the scheduled end of the regular season with no alterations to the postseason schedule needing to be made as a result. Nevertheless, the schedule could have been disrupted if rain-outs or other such events disrupted the schedule near the end of the season or on the day set aside for tiebreakers, and the tie-breaking procedure and scheduling would have become more complicated if three or more teams had tied. That would have required a series of one-game playoffs, taking more than one day. A series of one-game playoffs would have also been necessary if teams had tied for their division title also tied for the second wild card – in such a case, the division title would have been settled first, with the loser of that game then contesting a tiebreaker for the last wild card berth. There have been several occasions where such scenarios were possible as late as the last game of the season, but it never happened. To provide some additional flexibility in case of make-up games and/or complicated playoff scenarios, an additional break of one day was always scheduled between the wild card game and the start of the Division Series in each league.
Starting in 2012, with the Wild Card game between the top two teams who did not win their division, if two teams tie for a division title and both are in the playoffs, a one-game playoff was held because it would determine which team advances to the Division Series, and the loser would play in the wild card game only if its regular-season record since it was among the league's two best records for non-division-winners. When two teams tied for the top two wild card positions, an extra game was not held – performance-based criteria were used in that case to determine the home team for the Wild Card Game.