reliever

名词 reliever:

1. someone who takes the place of another (as when things get dangerous or difficult)
   同义词：stand-in, substitute, relief, backup, backup man, fill-in
2. a person who reduces the intensity (e.g., of fears) and calms and pacifies
   同义词：allayer, comforter
3. a pitcher who does not start the game
   同义词：relief pitcher, fireman