Doubleheader
Two games on the same day between the same clubs, almost always because weather took one earlier.
What it actually is. A doubleheader is two games played by the same two teams on one day. Modern ones are usually split, meaning separate admissions with the park cleared in between, and they are almost always the product of a rainout that has to be made up. A traditional doubleheader, both games on one ticket back to back, has become rare.
What somebody who knows the game gets out of it. A doubleheader is a roster problem before it is a baseball problem. It requires two starting pitchers on the same day, it drains a bullpen for the following week, and it forces a manager to rest regulars in a game that counts the same as any other. Clubs are allowed to add a pitcher for the day, which is what the twenty seventh man rule is for, and the deeper an organization's pitching depth is the less a doubleheader costs it.
The numbers worth knowing. A club plays a handful of doubleheaders in a normal season, concentrated in April and in cities with bad spring weather. Seven inning doubleheader games were used in 2020 and 2021 and then dropped; they are nine innings again.
What people get wrong about it. The two games are entirely separate. Statistics, ejections and lineups do not carry across, a player ejected from the first game can play the second unless the league says otherwise, and a suspended game resumed before a regular game is not the same thing as a doubleheader at all.
At Little League and travel ball. Youth and travel teams play the equivalent constantly, often three games in a Saturday. This is exactly why pitch count and rest rules exist, and why the Pitch Planner on this site is built around a weekend rather than a game: the constraint that decides a travel tournament is almost never talent, it is arms.
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