Sheets hasn't pitched since mid-july because of a finger injury on his throwing hand.
Sheets played catch in the outfield before the series opener last night, a 5-3 Brewers loss to the Cubs.
The Brewer starters have an ERa of 5.55 and Sheets is hoping to help turn the momentum back in the Brewers favor. Milwaukee has lost 5-straight games to fall 2 1/2 games behind the first place Cubs and a half-game behind second place St. Louis.
Sheets will fill the roster spot vacated by right-handed pitcher Claudio Vargas, who was placed on the 15-day disabled list with a lower back strain.