OAKLAND -- Yoenis Cespedes opened his Major League career with a flourish, hitting three home runs in his first four games. Then came a series of struggles before hitting another home run on Wednesday, in his 12th game.

"He's always a threat at the plate," A's manager Bob Melvin said. "He doesn't get down on himself. He's a tough kid and he's serious about baseball."

Cespedes' roller-coaster beginning is the result of opposing pitchers making adjustments, and then Cespedes making his own adjustments.

"Early on they saw what he could do with a fastball," Melvin said. "Now they are starting to see what he can do with a breaking ball. You can see how much he's learning, how much he is processing."

That includes the English language too, with help from teammate Jemile Weeks and coach Ariel Prieto.

"Every day he seems to have learned a new word or two," Melvin said. "He has more English in his repertoire than I have in Spanish, so he's ahead of me already."

Thompson claimed off waivers from Angels

OAKLAND -- Right-hander Rich Thompson was claimed off waivers from the Los Angeles Angels earlier Friday and made it to Oakland in time to be available for the series opener with the Cleveland Indians.

Thompson, who will wear No. 54, appeared in two games for the Angels this year, allowing four runs on five hits and a walk in 2 1/3 innings. He is 3-4 with a 4.24 ERA in 81 career appearances, all in relief.

To make room for Thompson, the A's optioned right-hander Neil Wagner to Triple-A Sacramento. Wagner was recalled by the A's on Tuesday but did not appear in a game with Oakland. He made three relief appearances with Sacramento and was 1-0 with a save, a 5.06 ERA and .273 opponents batting average.