What is the 27th man on an MLB roster and why does it exist?

Roster construction is one of the most interesting concepts of Major League Baseball. Casual fans of the sport may not always think about how many players are actually on a big-league roster.

It used to be that teams had 25 players on their roster for the regular season until September 1, when rosters expanded up to 40 players before being cut back down to 25 for the postseason. However, things have changed since then.

In 2020, a new rule went into effect that stated clubs must have exactly 26 players on their roster for the vast majority of the season until rosters expand.

But did you know that in certain cases, teams are allowed to feature one extra player on their roster, known as the 27th man? Major League Baseball offers an explanation for this rule.

How does the 27th man rule work?

When rosters were still 25 players, this was referred to as the 26th man. But with the new roster rules in place, that has changed.

An MLB team can only have a 27th man on their roster when a doubleheader is being played. Doubleheaders occur when a previously scheduled game is postponed for any reason, which results in the two teams playing two games against each other in one day down the line.

The 27th man accrues one day of Major League service time and is available to play in each of the two games. However, they must be sent back down to the minor leagues following the completion of the doubleheader. The promoted player must also come from a team's 40-man roster.

Typically, after being sent back down to the minor leagues, a position player must remain there for at least 10 days before being eligible to return to the Majors. Pitchers and two-way players must wait at least 15 days. That rule does not apply to the 27th man used for a doubleheader.

In other cases, teams can call up a 27th man when they are completing a previously suspended game and have another game following the completion of the suspended game.

The 27th man is not eligible to play in the suspended game. They are only eligible to play in the originally scheduled game.

Hopefully, we have cleared up any confusion on this matter.