The Oakland Athletics activated right-hander Kiko Calero from the 15-day disabled list Sunday. To clear room for Calero the A's optioned right-hander Seth Etherton to Triple-A Sacramento. Etherton was 1-1 with a 6.62 ERA during his stint with the A?s. Calero went on the DL on May 10 retroactive to May 9 with tendinitis in his right elbow.