MLB Roster Limits

Each MLB club is permitted to reserve no more than 40 players on its MLB Reserve List, which is why the MLB Reserve List is also called the "40-man roster."

Each MLB club is required to roster at least 25 players but no more than 26 players (formerly a 24 player minimum and a 25 player maximum limit) on its MLB Active List beginning on MLB Opening Day up through 11:59 PM (Eastern) on August 31st, and then 28 players (formerly a 24 player minimum and a 40 player maximum limit) beginning on September 1st and extending through the last game of the MLB regular season. A club's MLB Active List roster must revert back to 26 players again for post-season play (LDS, LCS, and World Series). 
NOTE: In the event of an unusual or unavoidable circumstance (such as a multi-player trade, multiple trades made at about the same time, and/or multiple waiver claims awarded at about the same time, where several players have been acquired but have not yet reported), a club's MLB Active List roster can temporarily go below 25 players (beginning on MLB Opening Day and extending through August 31st) or below 28 (beginning on September 1st and extending up through the conclusion of the MLB regular season), but for no more than 48 hours.   

If a player is placed on the MLB CoViD-19 Related Injured List or on the Restricted List as the result of not being vaccinated, the player can be temporarily replaced on the MLB Active List roster by any player in the organization. When the player on the CoViD-19 IL or Restricted List is reinstated, the replacement player can be reassigned back to the minor league affiliate from which he was selected without requiring an Optional Assignment or Outright Assignment.
NOTE-1: The replacement player accrues one day of MLB Service Time for each day spent on the MLB Active List, but is not charged with an optional or outright assignment when sent back to the minor league affiliate.
NOTE-2: If a pitcher starts a game and pitches at least four innings and then is subsequently placed on the CoViD-19 Related Injured List or on the Restricted List for not being vaccinated, he cannot be replaced on the Active List roster for at least four days.

If MLB regular season games are scheduled prior to MLB Opening Day (for example, if MLB games are played in Japan, Mexico, Australia, etc), the MLB Commissioner will determine the Active List maximum roster limit for those games.   

Prior to the start of each MLB regular season a club must designate all players on its Opening Day Active List roster as either a "position-player," a "pitcher," or a "two-way player" (but only if the player already qualifies as a "two-way player") and once so designated the player's position designation cannot be changed for the balance of that season unless a "position-player" or a "pitcher" subsequently qualifies as a "two-way player" and is so designated during the course of the season.  

A maximum of 13 players on an MLB Active List can be designated as "pitchers" (14 "pitchers" maximum when rosters expand from 26 to 28 beginning on 9/1). 

For players who are recalled from an Optional Assignment or who have their contract selected and are added to an MLB Active List during the MLB regular season, the club must designate the player as either a "position player," a "pitcher, or a "two-way player" (if the player already qualifies as a "two-way player") when the player is placed on the club's MLB Active List roster.
NOTE: Since there is no limit on the number of "pitchers" who can be on a minor league club's active list roster, the "position-player," "pitcher," and "two-way player" designations are not used in the minor leagues.  

A player designated as a "position-player" can pitch in a game only if his club is winning by at least ten runs in the 9th inning, or losing by at least eight runs at any time during the game,  or regardless of the score if the game has gone to extra innings.  

With approval of the MLB Commissioner, a "two-way player" on an MLB Active List who has undergone elbow UCL reconstruction (so called "Tommy John surgery") can be temporarily assigned as a "pitcher" to a minor league club for rehabilitation purposes while remaining eligible to play in MLB games as a "position-player."  

A "position player" or a "pitcher" can be designated as a "two-way player" (and does not count against the maximum 13 pitchers allowed) if the player has thrown at least 20 IP during the course of the current MLB season or threw at least 20 IP in either of the two previous MLB seasons - AND - has started at least 20 games as a position player (including DH) and with at least three plate appearances in at least 20 of the games started as a position-player in the current MLB season or started at least 20 games as a position player (including DH) and with at least three plate appearances in at least 20 of the games started as a position-player in either of the two previous MLB seasons.   

If a player who was designated a "two-way player" prior to the start of a season because he automatically qualified as a "two-way player" by virtue of meeting the "two-way player" requirements during a previous season but then was to fall below the IP and/or G/PA threshold by the end of the current season, he would not automatically qualify as a "two-way player" again at the start of the next season (he would count as a either a "position player" or a "pitcher" until he could re-establish himself as a  "two-way player").  

No more than 15 players (formerly no more than 16 players) on a club's MLB Reserve List (40-man roster) may be on Optional Assignment at any one time prior to September 1st, and no more than twelve players may be on Optional Assignment at any one time beginning on September 1st and extending through the conclusion of the MLB regular season.

"Position-players" who are optioned to the minors generally must remain on Optional Assignment for at least ten days and "pitchers" and a "two-way players" who are optioned to the minors generally must remain on Optional Assignment for at least 15 days. (A "position-player" optioned to the minors during Spring Training generally must remain on Optional Assignment for the first ten days of the MLB regular season, and a "pitcher" or a "two-way player" optioned to the minors during Spring Training generally must remain on Optional Assignment for the first 15 days of the MLB regular season).
EXCEPTIONS: The only exceptions are if the player is traded or claimed off waivers, recalled as the "27th man" for a doubleheader prior to September 1st (second game of the doubleheader only if two games were scheduled after a postponed or suspended game from the previous day) or other special circumstances, or is recalled to replace a player on the MLB Active List who is traded, claimed off waivers, or placed on the MLB Injured List, Bereavement/Family Medical Emergency List, or Paternity Leave List, or the Restricted List (but only pursuant to a suspension or administrative leave resulting from a violation or possible violation of the joint MLB-MLBPA JDV policy or a suspension resulting from a violation of the joint MLB-MLBPA JDPTP policy).

A club can recall a player ("position-player," "pitcher," or "two-way player") from a minor league Optional Assignment and place the player on its "Taxi Squad" for one day. If the player is not added to his club's MLB Active List by 3 PM (Eastern) the next day or at least three hours prior to the scheduled start of the next day's game (whichever is later), the player must be removed from the Taxi Squad and returned to his minor league assignment. A player on the Taxi Squad does not count against his club's MLB Active List or the minor league affiliate's active roster, and the player does not accrue MLB Service Time while on the Taxi Squad.
NOTE: The most common reasons to recall a player and place him on the Taxi Squad is when a club is considering whether to place a player on there Injured List (or other MLB inactive list) but has not yet decided, or if a trade is imminent but has not yet been consummated. 
CoViD-19 EXCEPTION: A club can carry up to five minor league players (one must be a catcher) on its MLB Taxi Squad who can be temporarily added to the club's MLB Active List roster to replace a player who is placed on the CoViD-19 IL.   

Prior to September 1st, a club can temporarily add one additional player (can be either a "position-player," a "pitcher," or a "two-way player") to its MLB Active List on any day where two games are scheduled (not including a day where the first game is the completion of a suspended game), as long as the second game was not scheduled as the result of a game that was postponed earlier in that series and rescheduled for the next day. If the postponed or suspended game was from earlier in the series and was rescheduled for the next day, the additional player can be temporarily added to a club's MLB Active List for the second game only. However, the 27th man can be active for both games of the doubleheader even if the postponed / rescheduled game was from the previous day as long as both clubs agree to the arrangement. Also, adding an additional player to a club's MLB Active List can be authorized by the MLB Commissioner for any game(s) involving unusual travel circumstances and/or any game(s) played in a non-MLB city or country.  

1. The extra player temporarily added to the club's MLB Active List 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.

2. The player temporarily added to the club's MLB Active List does not have to be a pitcher.

3. In the case of two games being scheduled on the same day where a player is temporarily added to a club's MLB Active List, the extra player cannot be switched between games.

4. A minor league player can be added to a club's Active List as the extra player even if he has not spent ten days (for a "position-player") or 15 days (for a "pitcher" or a "two-way player") on Optional Assignment (or Outright Assignment) prior to being added.
   
7. A player added to a club's MLB Active List as an extra player can remain on the Active List and a different player can be dropped the next day, as long as the extra player was not called up from the minors prior to spending at least ten days (for a "position-player") or 15 days (for a "pitcher" or for a "two-way player") on Optional or Outright Assignment. However, a player called up as the extra player prior to spending at least ten days (for a "position-player") or 15 days (for a "pitcher" or for a "two-way player") on Optional or Outright Assignment could remain on the club's MLB Active List roster if the player replaces a player who is placed on an injured list or other MLB inactive list the next day.    

8. If a player is temporarily recalled as an extra player and then is optioned or outrighted back to the minors the next day, the "10-day rule" clock (for "position-players") or "15-day rule clock" (for "pitchers" and for "two-way players") that prohibits a player from being recalled until he has spent at least ten days (for "position-players") or 15 days (for "pitchers" or for "two-way players") on Optional or Outright Assignment (unless he is replacing a player who is placed on an injured list or other MLB inactive list) does not start over again. However many days toward ten (for a "position-player") or 15 (for a" pitcher" or for a "two-way player") that the player spent on Optional or Outright Assignment prior to being recalled as an extra man counts toward the ten days (for a "position-player") or 15 days (for a "pitcher" or for a "two-way player").    

A player temporarily added to a club's MLB Active List for a doubleheader or other circumstances accrues one day of MLB Service Time.