The story of Garrett Mock today remains the same as it's been for the past few years. Nationals officials agree on his potential, his arm strength and his raw stuff. The phrase "best arm in the organization" is frequently bandied about. But after just 4 2/3 laregly troublesome innings, Mock is out of big league camp.

Mock, 27, allowed 11 runs (five earned), nine hits and six walks while recording those 14 outs. The neck surgery that he underwent and recovered from last year was not a factor — "I think he's finally 100 percent," Manager Jim Riggleman said. The Nationals have been trying for a few seasons, but they cannot quite figure out what is preventing Mock's stuff from producing the kind of results it is seemingly capable of.

"He's shown so many flashes," Riggleman said. "I can remember talking to an opposing manager in '09 after he pitched in a ballgame against a very good ball club. The manager was talking to me the next day, 'Our guys are raving about Garrett Mock's stuff. They didn't know anything about him.' He just dominated a very good lineup. And then maybe he takes a step backwards."

Last night, then, was a fitting end to his latest stay with the Nationals. Mock entered in the third inning with two men on base and made a mess of the inning, hits flying all over the field. And then he utterly shut down the Astros for an inning.

"It's very confusing," Riggleman said. "Last night, he gave up some hits, and then he was untouchable. That's kind of been what he can do. I think he's at the optimal age. It's time for Garrett to become a starting pitcher and get stretched out down there. If he comes back and joins us, great.

"It's a little mystifying at times. Last night he threw some pitches that the bottom dropped out of. Never mind hitting them, you could barely catch them. The swings and misses, there were a couple that hitters weren't even close. And then the next thing you know, they squared up a couple and hit them against the wall. It's in there for him to be a successful pitcher in the big leagues. He's just going to have to show us again."