1995: With MLB's realignment into three divisions per league the year before, the Division Series was born. The six division winners plus one Wild Card in each league are pitted in the best-of-five series. From 1995 through 2011, the Wild Card winner played the team with the league's best record, unless that team was in the same division, in which case it would face the second-best division winner.
2012: A second Wild Card per league was added, and the winner of the one-game playoff played the club with the best record in the Division Series. The restriction against teams from the same division playing each other was removed.