The move was made prior to the Athletics' 9-4 loss to the Los Angeles Angels. The loss put Oakland one game back of Los Angeles in the AL West.
Right-handed pitcher Dan Otero was recalled from Triple-A Sacramento in a corresponding roster move. Doolittle is 1-3 with 2.28 ERA, 80 strikeouts and 20 saves in 55.1 innings this season.
"I mean, I'm [upset], mainly because I can't be out there helping the team," Doolittle said to MLB.com. "But, on the other hand, coming down the home stretch, there's really no time to be [upset] or disappointed.
- Scooby Axson