The left-handed starter may not be ready to make a rehab start this week nor return to the Nationals as originally expected.
The left-handed hasn't started throwing yet, 11 days ahead of his expected return from the disabled list.
The Nationals hope the left-handed reliever will rest for over two weeks and be pushed to the back of the rotation after the all-star break.
As expected, the left-handed reliever with an ailing back lands on the disabled list for the second time this season.
Ross Detwiler will be placed on the disabled list, and Dan Haren will take his place in the rotation Monday.
Ross Detwiler's lingering back issues may force the Nationals to trade for a pitcher to stabilize the back of their rotation.
The left-hander threw a clean bullpen session, according to Davey Johnson.
Ross Detwiler says he has "no question" he'll start Wednesday, and Dan Haren throws a bullpen session.
Ross Detwiler could miss his next start with a lower back ailment.
The left-handed starter hasn't pitched since May 15.