Werth has setback, Detwiler to have second MRI

Outfielder Jayson Werth was expected to play in his second rehab game Thursday night in Potomac. Instead, the veteran right fielder has had a setback to his sore left hamstring. Werth will not be activated off of the 15-day disabled list Saturday, as was previously anticipated. On Wednesday night, Werth went 1-for-2, ran the bases and made a few defensive plays, showing no ill effects from his ailing hamstring. Afterwards, he said the hamstring felt "pretty good." But manager Davey Johnson told reporters Werth felt a "slight bit of tightness in the hamstring" after that rehab start. General manager Mike Rizzo told reporters in San Diego that they wanted Werth to play more rehab games before rejoining the team. That means his activation from the disabled list will be pushed back. Meanwhile, Johnson said on MASN's Nats Xtra postgame in San Diego that left-hander Ross Detwiler's MRI on his back came back with "irregularity." Rizzo confirmed to reporters that Detwiler will go in for another MRI to see if they can find out what is wrong with his back. Long relievers Craig Stammen or Zach Duke could take Detwiler's next start in San Francisco. But if the team finds out Detwiler needs to be placed on the disabled list, then a Triple-A call-up, such as veteran Chris Young, might be the call.