American League Divisional Series

In Major League Baseball, the American League Division Series (ALDS) determines which teams will play in the American League Championship Series (ALCS). It is played in a best-of-five format.

The Division Series was implemented in 1981 as a result of a midseason strike, with the first place teams before the strike taking on the teams in first place after the strike. After 1993, it was implemented for good when Major League Baseball restructured each league into three divisions. In 1981, a split-season format forced the first ever divisional playoff series, in which the New York Yankees won the Eastern Division series over the Milwaukee Brewers (who were in the American League until 1998) in five games while in the Western Division, the Oakland Athletics swept the Kansas City Royals (the only team with an overall losing record to ever make the postseason). The Yankees have currently played in the most division series in history, with eighteen appearances. In 2015 the Toronto Blue Jays and Houston Astros became the last teams to make their first appearance in the ALDS. The Astros had been in the National League until switching to the American League in 2013 and had previously made the NLDS 7 times.

From 1998 to 2011, the wild-card team was assigned to play in the division winner with the best winning percentage (outside of their own division) in one series, and the other two division winners met in the other series. However, if the wild-card team and the division winner with the best record were from the same division, the wild-card team played the division winner with the second-best record, and the remaining two division leaders played each other. Beginning with the 2012 season, the wild card team that advances to the Division Series was to face the number 1 seed, regardless of whether or not they are in the same division. The two series winners move on to the best-of-seven ALCS. Home field advantage goes to the team with the better regular season record (or head-to-head record if there is a tie between two or more teams), except for the wild card team, which never receives the home field advantage.

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