Volstad, who has not won a game in the big leagues in nearly a year, was optioned to Triple-A Iowa on Sunday to make room on the roster for Ryan Dempster, who was activated from the disabled list. Dempster had been sidelined since June 16 with a sore right lat.
Volstad, whose last Major League win was July 10, 2011, made a spot start for Dempster on Tuesday against the Braves and gave up six runs on seven hits over 4 1/3 innings. He had no problems in the first four innings, then gave up five runs in the fifth.
He will start for Triple-A Iowa on Thursday, Cubs manager Dale Sveum said Sunday.