Pitchers will now be required to face a minimum of three batters or complete the half inning before another pitcher can come into the game. Gone are the days of bringing in somebody for one out unless it is the final out of the half inning.
https://www.espn.com/mlb/story/_/id/28124981/how-mlb-new-three-batter-minimum-rule-impact-game
https://www.espn.com/mlb/story/_/id/28124981/how-mlb-new-three-batter-minimum-rule-impact-game