In Major League Baseball (MLB), extra innings are played when the score is tied after the completion of nine regulation innings. The game continues with both teams alternating turns to bat and field, starting with the visiting team batting in the top half of the inning and the home team batting in the bottom half. The innings proceed until one team leads at the end of a completed inning, or when the home team scores the winning run during its turn, which immediately ends the game in a "walk-off" manner.
During the regular season, a special extra innings rule is applied where each half-inning in extra innings starts with an automatic runner placed on second base. This runner is the player who batted immediately before the leadoff batter for that inning, often referred to as the "ghost runner." This rule helps shorten games and reduce player fatigue. Runs scored by the automatic runner are considered unearned for pitchers, so it does not affect their earned run average (ERA). This automatic runner rule was introduced during the 2020 pandemic season and has since been made permanent for the regular season.
However, in the postseason, MLB does not use the automatic runner rule. Instead, extra innings are played with bases empty, following the traditional rules where players must bat and run the bases as normal until one team wins the game. Additionally, pitchers in the postseason are required to face a minimum of three batters or finish a half-inning, a rule implemented to reduce pitching changes and speed up the game.
In summary, extra innings in MLB comprise additional innings played until a winner emerges, with the regular season featuring an automatic runner on second base in extra innings and the postseason playing traditional extra innings without that runner. The visiting team bats first in each extra inning, and the home team gets the chance to either tie or win the game in the bottom half of the inning.
