Nationals manager Jim Riggleman said a few minutes ago that Stephen Strasburg, who came out of his start on Saturday with a strained flexor tendon in his right forearm, won't make his scheduled start on Thursday. He will be evaluated further, and Riggleman said it's likely Strasburg will go on the 15-day disabled list.
If Jordan Zimmermann, himself coming back from Tommy John surgery, isn't called up from Triple-A Syracuse to take Strasburg's start against the Cardinals, Riggleman said one of the Nationals' long relievers (Miguel Batista or Craig Stammen) would fill the spot.

Strasburg, who pitched through similar symptoms in college, was evaluated in Philadelphia on Saturday night, and the Phillies' doctors told the Nationals that Strasburg was fine, and would be pitching in five days. "The MRI is less conclusive that he would be pitching in five days, so we're putting him on the DL," Riggleman said. If the news from further evaluations indicates that Strasburg only had "a little ache," Riggleman said the Nationals would think about letting him pitch again this year.
"It's just too early to tell," he said. "We've got at least 15 days before we would have to make that decision. We need to see what conclusively is said by the doctor when (Strasburg) gets looked at."
General manager Mike Rizzo is scheduled to address the media within the hour, so I'll have more at that point. You can also follow me on Twitter for additional updates.
UPDATE AT 5:38 P.M.: Nationals GM Mike Rizzo said Strasburg will have an enhanced MRI this week; his flexor tendon was swollen enough that a regular MRI didn't show a complete picture of his forearm and elbow. The Nationals will put Strasburg on the 15-day disabled list, and decide what to do with him the rest of the year after the enhanced MRI. They're still calling it a strained flexor tendon for now. "But to get a clear diagnosis, we've gone to the extreme of having an arthrogram (or enhanced MRI)," Rizzo said.
Rizzo said Strasburg came to the ballpark wanting to play catch today, but the Nationals told him they wouldn't allow him to do it. "He wants a resolution to find out what's going on," Rizzo said. "To say he was a little anxious and a little emotional would be fair to say."
Team doctor Wiemi Douoguih will give Strasburg the MRI; Rizzo said the Nationals are not planning for a second opinion as of right now. The injury is similar to the one John Lannan had in April.
As you can tell, the Nationals aren't ready to make any pronouncements on Strasburg's long-term plans yet. They've got two weeks to figure out what they want to do with him, and whether he pitches again this year will depend on what they see in the next MRI.
A team spokesman said Strasburg's enhanced MRI is not scheduled yet, but the Nationals are shooting for Thursday. Rizzo would not say who he plans to have start on Thursday, but Jordan Zimmermann seems to be the leading candidate.