If a player has acted as a courtesy runner for a pitcher, can they change to run for the catcher later?

A player serving as a courtesy runner for a pitcher is specifically designated for that role, and this commitment limits their ability to take on additional responsibilities, such as running for another player, like the catcher. The rules governing courtesy runners stipulate that once designated as a courtesy runner for one position, the player is not allowed to switch to run for another position during that inning or game. This ensures clarity and maintains the pace of play, allowing the game to flow smoothly without adjustments for multiple position changes for courtesy runners. Thus, the answer encapsulates the rules set forth regarding the use of courtesy runners in contexts like these, affirming the player's sole role in running for the pitcher without the leeway to change that status mid-game.