The Washington Nationals placed left-handed pitcher Ross Detwiler on the 15-day disabled list, retroactive to July 4, on Sunday with a lower back strain.
Detwiler, originally projected to start Monday's series opener at Philadelphia, is 2-7 with a 4.04 ERA in 13 starts. He experienced discomfort in his back when he threw his bullpen session Saturday.
Washington is expected to replace Detwiler in the rotation with right-hander Dan Haren. Currently on the DL with a shoulder injury, Haren is 4-9 with a 6.15 ERA in 15 starts.
The Nationals open a four-game series against NL East rival Philadelphia on Monday.