Three-batter minimum

From BR Bullpen

The three-batter minimum rule was adopted before the 2020 season in order to limit the number of pitching changes during a game. Previously, when a pitcher was replaced by a reliever, the new pitcher could only be changed once he had finished pitching to one batter, or one out had been recorded. This was contrary to pinch-hitters, who could be sent in at will, with the only limit being the number of available substitutes. With the introduction of the rule, the new pitcher now has to face a minimum of three batters until the completion of their at-bat, or until the completion of the inning. If the latter occurs after only one or two batters and the pitcher remains in the game to start the next inning, the rule still applies.

The purpose of the rule is to limit the number of pitching changes, and particularly the use of relief specialists who face only one batter before giving way to another pitcher. This was particularly the case for some left-handed relievers derisively called LOOGYS (or left-handed one-out guys) who hardly ever faced more than one or two left-handed hitters. With the introduction of the rule, LOOGYS still have a role, but they are now almost exclusively used to record the final out of an inning, at which point they can be replaced before the next inning starts. There was some concern that the rule would spell the end of such specialists, but it has not been the case.

The rule has had only limited effect on the pace of play, but it has eliminated some strategies that were detrimental to fans, when some managers would use three or four pitchers to complete an inning at a key point of a game, slowing the action to a crawl, causing numerous delays in the ballpark and an endless stream of commercials for those following the game on television or on the radio. Tony LaRussa was known as an egregious user of such a strategy, but outside of the postseason, he had few imitators.