In games using playing cards, a wild card is one that can be assigned any value its holder desires. A wild card can be a pre-assigned card, such as any 2 (deuce) or the jack of spades, for example, or a special card, usually one of the jokers. (See also Wild card (poker).)
In North American professional sports leagues, the term "wild card" refers to a team that qualifies for championship playoffs without winning their specific subdivision (usually called a conference or division) outright. The number of wild card teams varies. In most cases, the rules of the league call for the wild card team to to survive an extra round and/or to play the majority of their postseason games on the road.
Major League Baseball
In Major League Baseball, the wild card team must surrender the home field advantage in the Division Series (ALDS and NLDS) and the League Championship Series (ALCS and NLCS). Regardless, however, of how the League Champion team reaches the World Series, the home field advantage for the World Series has been determined beforehand (prior to 2003, on an alternating schedule; in 2003 and 2004 the home field advantage was determined by the winner of the All-Star Game). A controversy resulted in 1997 when the Florida Marlins, who won the National League pennant after qualifying for the playoffs as a wild card, had home-field advantage over the AL champion Cleveland Indians, who had won their division, in that year's World Series, which the Marlins won in seven games, winning the seventh and deciding game at home (this same scenario was repeated in 2004 when the wild-card Boston Red Sox had home-field advantage over the St. Louis Cardinals, a first-place team, and defeated the Cardinals in four games). Both of the teams that reached the 2002 World Series were wild card teams: The Anaheim Angels from the AL and the San Francisco Giants from the NL. The Angels won the series in seven games. Indeed, wild-card teams won three consecutive World Series from 2002 through 2004, as the 2003 champion, the Florida Marlins, was also a wild card.
The wild card team (which can be considered the fourth seed in an analogy to other sports' tournaments) usually plays the team with the best record in the league (which can be considered the first seed) in the Division Series. However, an MLB rule states that teams from the same division cannot face each other in the Division Series. Therefore, if the wild card team is from the same division as the team with the best record, then the wild card team will play the second-best team in the league, while the team with the best record will play against the third-best team. This was borne out in the 2005 NLDS, for example, when the division winners in the National League were (in order from best to worst regular season record) the St. Louis Cardinals, the Atlanta Braves, and the San Diego Padres, and the Houston Astros were the wild card team. Normally, the Astros would have opened their Division Series against the Cardinals while the Padres would have faced the Braves; however, the Astros and Cardinals are both in the National League Central Division, so the Astros faced the Braves while the Padres faced the Cardinals.
National Football League
In the NFL, each of the two conferences send two wild-card teams along with four division champions to its postseason. The first round of the playoffs is called the "Wild Card Round". In this round, each conference's two best (by regular-season record) division champions are exempted from play and granted automatic berths in the "Divisonal Round". The four division champions are seeded from #1 through #4, while the two wild card teams are seeded #5 and #6; within these seperations, seeding is by regular-season record. In the "Wild Card Round", the #6 team (a wild card team) plays against the #3 team (a division champion) and the #5 team (a wild card team) plays against the #4 team (a division champion). The division champions have automatic home-field advantage in these games. In the "Divisional Round", the winner of the game between the #6 and #3 teams, plays against the #2 team, while the winner of the game between the #5 and #4 teams, plays against the #1 team. The #1 and #2 teams are granted automatic home-field advantage in these games. See NFL playoffs.
In professional tennis tournaments, a wild card refers to a tournament entry awarded to a player at the discretion of the organizers. All ATP and WTA tournaments have a few spots set aside for wild cards for players who otherwise would not have made the main draw with their professional ranking. They are usually awarded to players from the home country, promising young players or players that are likely to draw a large crowd.
Though the National Basketball Association and National Hockey League include wild-card teams in their playoff structures, the term "wild card" is seldom used in the NBA or NHL; instead, each playoff team is most commonly denoted by its seeding position within the conference. The division champions within each conference are given the #1 through #3 seeds based on their regular-season records. The five wild-card teams are awarded the #4 through #8 seeds, also based on their regular-season records. The division champions (first, second, and third seeds) and the best wild-card team (fourth seed) are given home-field advantage in the opening playoff series, in which they face the eighth-, seventh-, sixth- and fifth-seeded wild card teams, respectively. The winner of the #1 vs. #8 series goes on to face the winner of the #5 vs. #4 series, while the winner of the #2 vs. #7 series faces the winner of the #6 vs. #3 series. Home-field advantage in each playoff series is granted by regular-season record. Notice that the winner of the #1 vs. #8 series will always play against a wild-card team in the second round of the playoffs; this is arranged deliberately to "reward" the #1 seeded team by giving it the most winnable matchups in the first and second rounds.