26th Man Rule
The 26th Man Rule was adopted as part of Major League Baseball's Collective Bargaining Agreement approved in November 2011 and went into effect at the start of the 2012 season. The agreement included a recommendation of Commissioner Bud Selig's special committee for on-field matters to allow teams to add an extra player to their rosters under specific circumstances, notably when a team is playing a scheduled doubleheader.
Jeremy Hefner of the New York Mets was the first player to benefit from this rule, when he made his major league debut in the first game of a doubleheader against the San Francisco Giants on April 23rd.
The particulars of this rule are as follows (courtesy of The Cub Reporter website):
Beginning on MLB Opening Day up through August 31st, a club can temporarily add (recall or select) a 26th player to its MLB Active List on any day where two games are scheduled, as long as the second game was scheduled at least 48 hours in advance. If the second game was scheduled less than 48 hours in advance, a 26th man can be temporarily added to a club's MLB Active List for the second game of the doubleheader only.
- The "26th man" must be on the club's MLB Reserve List (40-man roster) or has to be added to the club's 40-man roster that day.
- The "26th man" does not have to be a pitcher.
- In the case of a doubleheader that is scheduled at least 48 hours in advance, the 26-man Active List limit is in effect for both games of the doubleheader, but the "26th man" cannot be switched between games.
- A player can be added to a club's Active List as the "26th man" even if he has not spent the minimum required 10 days on optional or outright assignment prior to being added.
- The player who was recalled as the "26th man" can remain on the Active List and a different player can be dropped the next day, as long as the "26th man" was not called up prior to spending at least ten days on optional assignment. NOTE: A player called up as the "26th man" prior to spending at least ten days on Optional Assignment could remain on the 25-man roster if the player replaces a player who is placed on the Disabled List (or other MLB inactive list) the day after the doubleheader.
- If a player is recalled as the "26th man" and is optioned back to the minors the next day, the "10-day rule" clock (prohibiting a player from being recalled until he has spent at least ten days on Optional Assignment, unless he is replacing a player who is placed on the DL or other MLB inactive list) does not start over again. However many days toward ten that the player spent on Optional Assignment prior to being recalled as the "26th man" counts.
- A player recalled as a "26th man" accrues one day of MLB Service Time.
The rule is sometimes refered to as the taxi squad, although that term has a wider meaning.