The Athletics placed Lopez on the 15-day injured list Tuesday with a left elbow flexor strain.
Lopez's strained elbow played a factor in his performance in a loss to the Mariners on Sunday, when he surrendered nine earned runs in just two innings. The Athletics will shut down for a period of time before he's cleared to start a throwing program, though the team is optimistic that the 27-year-old southpaw will make it back before the end of the season, likely as a reliever. Mason Barnett was selected from Triple-A Las Vegas to take Lopez's place on the active roster, but the team hasn't yet announced who will replace Lopez in the rotation.