The A's sent southpaw Brett Anderson to the disabled list on Tuesday as part of a compound roster move that also helps round out their bench.
Oakland also optioned reliever Edwar Ramirez to Triple-A Sacramento on Tuesday and recalled infielder Steve Tolleson and catcher Landon Powell to take up reserve roles with the parent club.
Anderson, who left his last start with tightness in his left elbow, threw once on the side before Oakland reached its conclusion. The left-hander was diagnosed with inflammation in his left elbow and a proximal medial forearm strain. Anderson, who recently agreed to a four-year contract extension with options for 2014 and 2015, is 1-1 with a 2.35 ERA through four starts.
Ramirez, meanwhile, has struggled with his control this season. The right-handed reliever is 1-0 with a 4.50 ERA through six appearances but has issued eight walks in 10 innings, which is tied for fifth among AL relievers.
Powell will be back with the A's for his second stint this season. The switch-hitter spent the entire 2009 campaign with the A's, but he started this season with Sacramento and has only spent two days with Oakland. Powell, who was hitting .222 with a home run and six walks for Sacramento, was briefly with the A's after Mark Ellis went to the disabled list.
Tolleson, the son of former utility man Wayne Tolleson, has yet to make his big league debut. The infielder was batting .333 with a home run and eight RBIs in 16 games for Sacramento, and he's seen time at third base, second base and shortstop.
Spencer Fordin is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.