Tanner Roark before Tuesday’s game. (Alex Brandon/AP)

On Sunday, Tanner Roark got the news he had only dreamed about. Class AAA Syracuse Manger Tony Beasley informed Roark he had been called up to the major leagues. But there was a catch: it wouldn’t happen until Tuesday so the right-handed pitcher had to keep it private until then.

“I was doing my best to keep it quiet,” Roark said standing at his new locker at Nationals Park, which didn’t have a name plate yet. “I told my parents. I told them to keep it quiet. I told my fiancée. That was about it.”

On Tuesday morning, Roark made the trip from upstate to Washington, after two days of anxious waiting and a lifetime of work. “I get to play with all the big boys and everything,” he said. “It feels good and I feel excited. Glad to be here.”

The Nationals called up Roark, 26, from Syracuse as insurance for Ross Ohlendorf, who landed on the disabled list over the weekend with right shoulder inflammation. Ohlendorf tossed only 15 pitches on July 31 because of a tired arm that hadn’t recovered from his previous appearance, a 114-pitch start on July 26. The veteran was outstanding  since he joined the Nationals, posting a 1.85 ERA over 34 innings as a long reliever and spot starter. Roark, who has filled both roles in the minor leagues this season, will be asked to fill Ohlendorf’s spot.

Manager Davey Johnson values Roark’s ability to carry a heavier load if needed. “Needed a more-innings guy,” Johnson said.

Roark, who was invited to big league camp this spring, began the season with Syracuse in the bullpen. In 22 relief appearances, mostly as a long reliever, Roark struck out 8.5 strikeouts per nine innings and posted a 2.40 ERA. He also stranded 10 of 11 inherited runners. It was his longest stint in the bullpen since 2009 in high-Class A when he was in the Texas Rangers organization.

(The following year, in July 2010, he and fellow Syracuse reliever Ryan Tatusko were acquired by the Nationals for infielder Cristian Guzman.)

But after there were a flood of doubleheaders because rainouts at Syracuse early this season, Roark was used as a starter. He pitched well enough to earn a spot in the starting rotation and has thrived. In his past 10 games, eight of them starts, he has a 2.05 ERA over 52 2/3 innings and has a struck out 33 while walking only four.

Overall, Roark has a 3.15 ERA over 33 games, 22 of them as a reliever, this season. He has a 0.994 WHIP (best in the International League), a strong 4.20 strikeout-to-walk ratio and opponents are batting just .217 off him (tied for first in the International League). Roark throws a mid-90s fastball with a sharp curveball and standout change-up.

Roark said he felt like he hit a groove last season, when he started worrying only about staring at the catcher’s glove and throwing to it. “It’s just attacking is what I got out of the bullpen and what I brought as a starter,” he said. “To keep attacking and keep the pressure on them and keep the hitter off balance. Just pounding the strike zone.”

For now, Roark will serve as the team’s long reliever and spot starter. Ohlendorf is eligible to come off the disabled list on Aug. 16. Ohlendorf played catch Tuesday afternoon and said he is “feeling better every day.” Johnson said Ohlendorf will throw a bullpen session but that depends on how the right-hander feels, but Ohlendorf said he hopes to throw the session on Wednesday. After that, Ohlendorf would need a rehab assignment, Johnson said.

Ohlendorf was the prime candidate to take over rookie right-hander Taylor Jordan’s spot in the rotation when he will be shut down after about four more starts in his first full season back from Tommy John surgery. If Ohlendorf needs more time and Jordan is shut down before then, Johnson said Roark would be the replacement. Injured left-handed stater Ross Detwiler was transferred to the 60-day disabled list to make room for Roark on the 40-man roster. Roark said he has no preference between relieving or starting.

“As long as I’m up on the mound and can compete and get to pitch,” he said. “That’s all I worry about.”