Softball, while similar to baseball, has many crucial differences, including its substitution rules. In baseball, when a player is taken out of the game, he can't re-enter. This is partially due to the high number of active players on a baseball roster, which can be 24 or more. However, in softball, there are fewer active players, so their substitution rules are more flexible.
She's Out, She's In, She's Back In Again
Any player in the starting lineup who gets taken out can return -- once. The most common occurrence is when a slow runner reaches base. A coach has the option to put a fast runner on in her place with the hopes that speedier player will come around with a run. At the end of the inning, the slow runner will go back to her fielding position, and the runner can't go back in the game. Softball pitchers can be taken out once as well, and can return to the mound later without having to play another position. Another kind of sub can take place before the game. Softball allows a designated player, much like the designated hitter in baseball. Unlike baseball, the designated player isn't necessarily hitting for the pitcher. Coaches may use the dp to hit for any position player.