Strong Finisher

From MLB Power Pros Wiki

The blue pitchers ability, STR Finisher, or Strong Finisher, this ability is good for starters, great for relievers and excellent for closers. It makes finishing games easier. The pitcher will pitcher better than usual in the latter innings, instead of tiring out. There may be a velocity boost and improved control.

There is a typo in the game when you receive this ability. It's labeled Starter Finisher.