Washington Nationals pitcher Ross Detwiler has been placed on the 15-day disabled list with a right back muscle strain, the team announced Monday.
He originally sustained tightness in his lower back on May 15. Detwiler, who is also dealing with a right oblique strain, is 2-4 with a 2.76 ERA over eight starts this season.
The Nationals recalled fellow left-hander Xavier Cedeno from Triple-A Syracuse, but the team is still searching for a starter to replace Detwiler on Tuesday versus the Orioles.
Cedeno went 1-0 with a 1.74 ERA in 10 relief appearances this season with Syracuse. He began the year with Houston, where he allowed eight runs in 6 1/3 innings, before Washington selected him off waivers on April 23.