WASHINGTON -- So far in his young career, 26-year-old Garrett Mock has been the pitching equivalent of a utility man.

He's been asked to throw multiple innings of relief, he's been called upon to record a single out and he's been slated as a fill-in starter.

During his up-and-down time between the Nationals and Triple-A Syracuse, Mock has had his share of disappointments and successes. In the Majors to begin the season, he was ineffective, wearing a 6.92 ERA. As a consistent starter in Syracuse this season, he has done enough to earn a spot in the Nationals' revolving rotation.

"[Mock] did everything we asked," interim general manager Mike Rizzo said. "He dominated in eight starts [at Syracuse]. He was off the charts, pounding the strike zone."

Mock, who was 5-1 with a 1.52 ERA as a starter in Triple-A (compared with a 17.18 ERA in five games as a reliever), is scheduled to pitch on Sunday in the finale of a four-game set against the Cubs.

"I've [started] more, but it always goes back to, what does the team want me to do?" Mock said. "They let me go down there [at Syracuse] to start, and I felt more comfortable doing that, and now I have an opportunity up here."

Mock's break has come in part because of his performances as a starter in Triple-A, but also due to the struggles of Ross Detwiler. A 23-year-old southpaw, Detwiler leapfrogged from Double-A to the Majors and struggled at the tail end of his winless, 10-start tenure.

Mock threw 41 innings for the Nationals last season, mostly as a reliever. He took the loss in three spot starts.

But Rizzo said that he always evaluated Mock as a starting pitcher, ever since Rizzo's former team, the D-backs, drafted him out of the University of Houston in 2004.

Former pitching coach Randy St. Claire liked Mock as a reliever, but when St. Claire was relieved of his duties in June, the organization turned Mock back into a starter.

"All of us in the front office thought his niche was as a starter," Rizzo said.

Now Mock has his Triple-A triumphs to use as a kind of blueprint for success at a higher level. He is intent on throwing pitches over the plate, down in the zone, to extract ground balls from hitters.

"He's got outstanding stuff," said pitching coach Steve McCatty, who was at Syracuse with Mock during parts of April and May. "His velocity is good, [he has a] good sinker and his offspeed is good. It's all about getting him to believe in his stuff and throw strikes all the time."

Whereas young pitchers Detwiler and Shairon Martis have started and struggled, leading to their demotions, Rizzo believes that Mock can be a starter for the Nationals for the long haul. Mock does, too, now that he is in his comfort zone.