The 26 Man and 40 Man Rosters
Twenty six men can play today, forty are under major league control, and the gap between those numbers is where most transactions happen.
What it actually is. The active roster is 26 players, with a limit of 13 pitchers. The 40 man roster is every player under major league contract, including those in the minors, and a player must be on it to be called up. Rosters expand to 28 in September. Adding somebody to the 40 usually means removing somebody else.
What somebody who knows the game gets out of it. The 13 pitcher limit is one of the most consequential quiet rules in the modern game, because it was introduced specifically to stop the bullpen from eating the bench. Before it, clubs were carrying 14 or 15 arms and playing with a three man bench, and pinch hitting had nearly disappeared. Roster rules are a major lever on how the game is played, and they are almost never discussed as such.
The numbers worth knowing. 26 active, 13 pitchers maximum, 40 under control, 28 in September with a 14 pitcher cap. A club makes a few hundred transactions in a season.
What people get wrong about it. The 40 man roster is where the real squeeze is. A club with a full 40 has to designate somebody for assignment to add anybody, which risks losing that player entirely, and that is why good players occasionally appear on waivers for nothing.
At Little League and travel ball. Travel rosters have their own version of this in roster lock rules: when the roster is frozen for a tournament, who counts as a guest player, and how many are allowed. Those rules vary by sanction and are covered in the travel section of this site.
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