A Nippon Professional Baseball roster is a list of players who are allowed by NPB Agreement to play in Nippon Professional Baseball's first leagues, the Central League and the Pacific League (NPB Agreement, Article 81).[1] This list is created from each team's Registered players under control (NPB Agreement, Article 52).,[1] and can be arbitrarily registered and unregistered at any time during the season (NPB Agreement, Article 85).[1] Also, the results of the list changes are announced by the NPB organization every day during the season and can be viewed.[2]
Players registered on the list are also said to be First squad player, and play in the first squad Central League and Pacific League. Other players are called Second squad players and Third squad players, and play in the second squad Eastern League and Western League, and play in unofficial games with independent leagues (NPB Agreement, Article 81, and Article 170).[1] However, unlike the relationship between major leaguers and minor leaguers in the Major League Baseball (MLB), the 1st, 2nd, and 3rd squad players all belong to the same team, and the only differences in contracts are the annual salary and contract period for each player.[3] Also, as mentioned above, if 10 days have passed since the player's registration was deleted, the team can re-register the player at any time during the season (NPB Agreement, Article 85).[1] For this reason, it is often seen during the season that main pitchers and main players are repeatedly deleted and re-registered for strategic reasons such as reorganizing the rotation of starting pitchers.[4]
Currently (2022 season), up to 31 players can be registered due to special measures to prevent the spread of infection due to the effects of COVID-19, and up to 26 of them can enter the bench.[5]
(Example: fielder 1 and pitcher 3 or fielder 2 and pitcher 2 or fielder 3 and pitcher 1)
Currently (2022 season), up to 5 foreign players can be registered. However, there are only four conventional players who can enter the bench.[6]
In the Japan Series, this system does not apply because a roster of 40 players is created and players are selected from among them.[7]
It refers to a measure that allows players who need to be deregistered due to suspected concussion to return even if it has not been 10 days since deregistration. Players who are eligible for concussion exemptions or who have been designated as replacements are allowed to return within 10 days.[9]
When a retired player participates in an official match as a retirement match, the player can be added to the team's player registration only on the day of the retirement match (limited to one day).[10]
Currently (2022 season), up to 31 players can be registered.[5] And up to 5 foreign players can be registered. However, there are only four conventional players who can enter the bench.[6] Players suspected of having COVID-19 who have been de-enrolled may be re-enrolled within 10 days if they test negative.[11]