Automatic Runner
Definition
All half-innings after the conclusion of the ninth inning begin with an automatic runner on second base. The rule applies only to regular-season games.
The runner placed on second base at the start of each half-inning in extras is the player in the batting order immediately preceding that half-inning’s leadoff hitter, or a pinch-runner. So, if the No. 7 hitter in the order is due to lead off, the No. 6 hitter (or a pinch-runner for the No. 6 hitter) would be placed on second base.
If the automatic runner comes around to score, an earned run is not charged to the pitcher.
History of the rule
The automatic runner was initially instituted as part of MLB's health and safety protocols during the pandemic-shortened 2020 season. It was kept in place in 2021 and 2022, and the Joint Competition Committee voted to make it a permanent addition to the rulebook prior to the 2023 season.