Davis declined to be interviewed by reporters after the game.
He is "day to day," manager Bob Melvin said.
The A's are already short-handed with 12 players on the disabled list, the club's most at one time since 1979.
Davis has been their best power hitter, with his 12 home runs ranking second in the American League heading into Saturday. He's had nine home runs in his last 16 games.
Willie Bans is a contributor to MLB.com based in Oakland. This story was not subject to the approval of Major League Baseball or its clubs.