reliever
US /rɪˈliː.vɚ/
UK /rɪˈliː.vɚ/

1.
a person or thing that provides relief from pain, distress, or difficulty
:
•
The cool compress was a great reliever for her headache.
•
He acted as a reliever for the stressed team members.
2.
in baseball, a pitcher who comes into the game to replace another pitcher, usually in the later innings
:
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The coach brought in a new reliever in the eighth inning.
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The team's bullpen has several strong relievers.