In a typical season, 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. Clubs are not limited to how many pitchers they may carry on the 26-man roster, and clubs typically will roster 12 to 13 pitchers vs. 13 to 14 position players (for a total of 26 active players), though the breakdown varies from team to team throughout a season.
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.
Prior to the 2020 season, a rule was agreed upon -- but not yet enacted -- preventing position players from pitching 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.
The two-way player rule has yet to take effect, though players are able to gain two-way-player status for the 2022 season if they appear in 20 games as a pitcher and start 20 games as a position player in 2021.
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.
Rules for 2021 season
Clubs are permitted to carry up to five additional Taxi Squad players on all road trips with the Major League team. If the club elects to carry five additional players, at least one must be a player whose designated position prior to the season is catcher. Players on the Taxi Squad are permitted to work out with the Major League club but are not permitted to be in uniform and in the dugout during games. Upon the conclusion of each road trip, players on the Taxi Squad will return to their club's Alternate Training Site.
Any clubs that experience a COVID-19 outbreak among their players may add to their Major League Active List temporarily, without the need for those players to be placed on waivers, outrighted, or optioned in order to be removed from the 40-man roster when players return from the COVID-19 Related Injured List.
The universal designated hitter did not return for 2021 after debuting last year. That means the DH will only be used in AL ballparks, while pitchers are back to hitting in NL ballparks.
Prior to the 2020 season, a rule was enacted to limit the number of pitchers a club can carry to 13, but the rule was not put into effect last year and continues to be on hold for 2021.
The aforementioned two-player rule, whereby all players qualify as a hitter, a pitcher, or a two-way player, was placed on hold for 2021. As a result, there are no rules limiting when a position player may pitch in 2021.