means relievers are pitchers who enter mid-game to hold a lead, escape a jam, or mop up a blowout, instead of starting it.

from baseball once treated pitching as a marathon, starters expected to finish what they began; the specialist role emerged in the mid-1900s as teams realized fresh arms late in games beat tired ones, and by the 1980s closers and setup men had turned the bullpen into its own ecosystem.