reliever
A baseball pitcher who comes in after the starter.
A reliever is a baseball pitcher who enters the game after the starting pitcher has been removed. While the starting pitcher begins the game and typically pitches for several innings, a reliever comes in to finish it. Teams often use multiple relievers in a single game, each pitching for just an inning or two.
The most important reliever is called the closer, who usually pitches the final inning when their team is winning by a small margin. These high-pressure situations require pitchers with strong nerves and excellent skills. Other relievers might enter earlier: a setup man pitches the eighth inning to prepare for the closer, while a long reliever might pitch several innings if the starter struggles early.
Being a reliever requires a different mindset than being a starter. Relievers must stay ready throughout the game, warming up quickly when called, then performing immediately under pressure. They might pitch several games in one week, unlike starters who pitch every five days or so.
Outside baseball, reliever can describe anyone who provides relief or takes over for someone else. A substitute teacher is a reliever for the regular teacher. When your friend tags you out during a long game, you might call them your reliever.