A club's 26-man roster is its full roster of active Major League players from Opening Day through Aug. 31, and during the postseason. From Sept. 1 through the end of the regular season, all clubs must carry 28 players.
Players on the 26-man roster (or the Major League injured list) accrue Major League service time. All players on the 26-man roster must also be on the 40-man roster. Teams are required to have a minimum of 25 players on their 26-man roster.
The number of pitchers a club can carry on the active roster is capped at 13 (14 from Sept. 1 through the end of the regular season). To adhere to that rule, clubs will have to designate each player as either a pitcher or a position player prior to each player's first day on the active roster for a given season. That designation cannot change for the remainder of the season.
Position players will not be allowed to pitch except in the following scenarios:
• They are designated as a "Two-Way Player." A player can only qualify for this designation if he accrues at least 20 Major League innings pitched and at least 20 Major League games started as a position player or designated hitter (with at least three plate appearances in each of those games) in the current or prior season.
• A game goes into extra innings.
• A player's team is losing or winning by more than six runs when he enters as a pitcher.
In the case of doubleheaders, clubs are allowed to recall one additional player who is on the 40-man roster to serve as the 27th member of the active Major League roster only for the day of said doubleheader. That player accrues one day of MLB service time and is returned to the Minor Leagues following the completion of the doubleheader. Teams also are permitted to call up a 27th man on days when they are completing a previously suspended game and have another game scheduled after that, but the 27th man is only permitted to play in the regularly scheduled game that day, not the contest that was previously suspended.
Upon being optioned to the Minor Leagues, a position player must remain there for a minimum of 10 days before he is eligible to be recalled to the Major League roster. For pitchers, the minimum is 15 days. If a player is serving as the 27th man for a doubleheader or replacing a player who has been placed on the injured list, there is no minimum number of days for which the optioned player must remain in the Minors.
Prior to 2020, the active roster size from Opening Day through Aug. 31 (and during the postseason) was 25 players. Players didn't need to be designated as position players or pitchers, and there wasn't a limit to the number of pitchers a team was able to carry.
A team needed to carry a minimum of 24 players on the active roster, and was permitted to carry 26 for doubleheaders. The minimum number of days a player needed to remain in the Minors after being optioned was 10, for all players.
On Sept. 1, teams were permitted to carry up to 40 players on their active roster until the start of postseason play, at which point the maximum reverted back to 25. All players added to the active roster during this period were required to be on the 40-man roster.