<P> A postseason roster takes effect only if a team clinches a playoff berth . Players who are part of the team's final roster at the end of the regular season are eligible to participate in the postseason . Any player who has been traded from a different team, spent time in the Minor Leagues, or signed later in the season with the team (no later than August 31) is eligible to participate in the postseason . A postseason roster is allowed up to 25 active players . Other players who are not on the 25 - man active roster will be assigned to the postseason secondary squad . Players who are on the disabled list or any other non-active transaction by the end of the regular season will have their transactions passed on in the postseason . Rosters for a series are set at the beginning of the series and no changes to the 25 - man active roster are allowed except when a player is moved to the disabled list or any other inactive transaction . If a player is moved to the disabled list or another inactive transaction during a series, he then becomes ineligible to be returned to the 25 - man active roster for the remainder of the series as well as the next series if applicable . If any player goes on any inactive transaction, any player from the 40 - man roster can be promoted to the 25 - man active roster for the remainder of the series if applicable . </P> <P> For a player to be eligible for the postseason active roster, he must have either been on his club's expanded roster or disabled list as of midnight ET on August 31 of that year and not placed on the 60 day disabled list after August 1 . The one exception is for replacing players on the disabled list . Since the 2014 season, an injured player eligible for postseason play may be replaced by any player within his club's organization, including players assigned to the club's minor league affiliates who are not on the major league 40 - man roster . Prior to 2014, only players who were on a club's 40 - man roster (including those added to the expanded roster after August 31 who would not otherwise be eligible for the postseason) at the conclusion of the regular season were eligible to replace injured players on postseason rosters . The 2015 Kansas City Royals were the first club to exploit this new provision when they added Raúl A. Mondesí--who at the time was assigned to the Royals' Double - A affiliate and was not on the 40 - man roster--to their World Series roster . </P> <P> All other professional players affiliated with Major League Baseball are signed to minor - league contracts . They can receive an invitation to spring training with their organization's Major League team without being on the 40 - man roster . Two types of players generally receive a non-roster invitation: prospect players who are there to gain experience and face tougher competition as well as receive instruction from the Major League team's coaching staff; and veteran players who were not offered any major league contract by a club . The veteran player is usually signed to a "two - way" salary option--one for their time in the minors and another if they are placed on the 40 - man during the season . All spring training invitees are under some sort of contract, to avoid liability if an injury were to occur to the player . </P> <P> Since 1933, an annual Major League Baseball All - Star Game referred to as the "Midsummer Classic", has been played (except 1945) during the "All - Star break" at the middle of each baseball season . The game features an American League (AL) All - Star team versus a National League (NL) All - Star team . </P>

How many players travel with a mlb team