The wild card format was introduced in Major League Baseball in 1994 when the league also split into three divisions. Each league had four playoff teams (the three division winners and one wild card) until 2012.
In 2012 a second wild card team was added, bringing the number of playoff teams to five in each league. Under the new format, the two wild cards in each league play a one-game playoff, the winner advancing to the League Divisional Series against the division winner with the best record.
Thus far, twelve wild card teams have won the pennant. That’s twelve teams in 25 seasons (through 2019). Since there were 50 pennant-winners in those seasons, that means wild card teams have won 24 percent of the pennants. A normal distribution would see the wild card win about 23 percent, so they’ve outperformed that a bit.
Wild card teams are 25-25 in their first round series (all of which have been best-of-five format). They are 13-12 in the LCS and 6-6 in the World Series, pending the outcome of the 2019 World Series.
Overall, wild card teams have won 44 of the 87 postseason series they’ve played through the 2019 ALCS.
Twice, in 2002 and 2014, both pennant-winners were wild card teams. Here are the twelve wild card teams to win a pennant and how they fared in the World Series.
Major League Baseball wild card teams who won the pennant
1997 Florida Marlins
Defeated the Indians in seven games in the World Series
2000 New York Mets
Lost to the Yankees in five games
2002 Anaheim Angels
Defeated the Giants in seven games
2002 San Francisco Giants
Lost to the Angels in seven games
2003 Florida Marlins
Defeated the Yankees in six games
2004 Boston Red Sox
Defeated the Cardinals in four games
2005 Houston Astros
Lost to White Sox in four games
2006 Detroit Tigers
Lost to the Cardinals in five games
2007 Colorado Rockies
Lost to the Red Sox in four games
2011 St. Louis Cardinals
Defeated the Rangers in seven games
2014 San Francisco Giants
Defeated the Royals in seven games
2014 Kansas City Royals
Lost to the Giants in seven games
2019 Washington Nationals
Will face the AL champion in the 2019 World Series.