Updated: 8/24/2014 6:15 pm
Oakland, CA (SportsNetwork.com) - The Oakland Athletics placed pitcher Sean Doolittle on the 15-day disabled list Sunday with a strained right intercostal.
Doolittle felt pain in his side while he recorded his 20th save of the season during Saturday's 2-1 win over the Los Angeles Angels of Anaheim.
In 54 relief appearances this season, the left-hander is 1-3 with a 2.28 earned run average. He has also issued just five walks and has 80 strikeouts, leading MLB relievers in strikeout-to-walk ratio.
Oakland also recalled reliever Dan Otero from Triple-A Sacramento. Otero went 7-1 with a 2.28 ERA over 56 games before being optioned to Sacramento on Thursday.