DiNardo, who opened last season as a member of Oakland's bullpen but eventually settled in as the No. 5 starter, also opened this season in the bullpen and again was moved into the starting rotation -- he went 1-1 with an 8.69 ERA in two starts -- before being optioned to Triple-A Sacramento.
Recalled to Oakland on Tuesday after going 3-1 with a 5.25 ERA in four starts for Sacramento, DiNardo is back in the bullpen for now, joining fellow former River Cats starter Dallas Braden and setup man Alan Embree as southpaw relief options for manager Bob Geren.
"He gives me flexibility," Geren said of DiNardo. "Him and Dallas can work in middle to long relief, so if I want to use Dallas for one or two hitters, I can."
DiNardo's presence also will allow Geren the luxury of using righty Chad Gaudin, a former reliever who was bumped from the starting rotation when Rich Harden came off the disabled list, more frequently.
"I can use Chad in shorter stints and still have some length [from DiNardo available]," Geren said. "Chad's been a short reliever before -- and a very good one -- so you might see more of that from him, especially with Santiago [Casilla] out."
Casilla, Oakland's top short reliever for the first six weeks of the season, is on the disabled list with a mild ligament strain in his right elbow and isn't expected back for at least another seven to 10 days.
Mychael Urban is a national writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.