WASHINGTON -- Tanner Roark knew on Sunday that he would soon be leaving Triple-A Syracuse to join the Nationals, but he was told to keep the news quiet. He told his parents and his fiancee, but otherwise was forced to wait until the move was officially announced.

That moment came on Tuesday, when the team optioned reliever Xavier Cedeno to Syracuse and transferred Ross Detwiler to the 60-day disabled list to make room for Roark on the 40-man roster. The 26-year-old right-hander said the news is only just beginning to sink in.

"It's so surreal," he said before Tuesday's game against the Braves. "At first when I got the call and [Syracuse manager] Tony Beasley told me, I was like, 'Wow. OK, this is what I dreamed for.' And then it started to sink in."

Roark, who was acquired from the Rangers in exchange for Cristian Guzman in 2010, was 9-3 with a 3.15 ERA in 33 appearances (11 starts) at Triple-A this season.

Manager Davey Johnson views Roark as a replacement for Ross Ohlendorf, who went on the 15-day disabled list on Sunday with right shoulder inflammation. Johnson said that Roark will also be a candidate to start when Taylor Jordan is shut down for the season if Ohlendorf and Detwiler are both still on the disabled list.

"[We] just need some more innings," Johnson quipped.

Roark acknowledged that coming out of the bullpen takes a different mentality, but he doesn't have a preference between starting and relieving.

"As long as I'm up on the mound and I can compete and pitch, that's all I worry about," he said.

Nats having issues with holding runners, allowing steals

ATL@WSH: Johnson on Strasburg, Clippard in 3-2 defeat

WASHINGTON -- In the fifth inning of the Nationals' loss to the Braves on Monday night, Stephen Strasburg got into a predictable rhythm and Braves outfielder Justin Upton took notice. Upton went for the steal and was halfway to second base before the ball even left Strasburg's hand.

Freddie Freeman followed with a single, scoring Upton to give the Braves a 2-1 lead in what became a 3-2 victory for Atlanta.

"It happens," Strasburg said dismissively after the game. "You get caught in having a predictable time to home plate, and he took a gamble. Three-and-0 hacking, they went up the middle. It is what it is."

The play was indicative of a larger trend that has haunted the Nationals this season: an inability to hold runners and a tendency to give up stolen bases. Entering Tuesday, the Nationals had only thwarted 10 stolen-base attempts all season and allowed 73 steals, the third most in the National League.

Washington's caught-stealing percentage (12) is by far the lowest in the Major Leagues. The next lowest is the Angels' 20 percent, and the Major League average this season is 28 percent.

"It's a tough thing," catcher Kurt Suzuki said. "You've got a lot of runners that nowadays they don't run unless they know they're going to be safe, so it puts you in a tough spot. All we can do is keep working on it. If you try to rush it and stuff, you start making errors, so you can't try to change too much."

The catchers are partially to blame, as their throws to second base have sometimes been off target. Suzuki has thrown out six runners while allowing 49 steals. Wilson Ramos has thrown out four and given up 18 steals.

However, manager Davey Johnson said most of the problem stems from the pitching staff. Opponents have stolen 12 bases with Strasburg on the mound and 11 against Jordan Zimmermann. Reliever Drew Storen was demoted to Triple-A Syracuse last month in part because of his slow time to the plate.

"Stras has probably given up a whole bunch because he's pretty much set in his timing, but some guys are very slow," Johnson said. "We had that problem last year, the same thing. We spent a lot of time in the spring going over how to be a little quicker, but basically, they're stealing off our pitching."

Suzuki added that there's only so much you can change without disrupting a pitcher's performance.

"You don't want to do that, get out of their comfort zone and then leave a pitch over the middle of the plate and it's hit for a homer," he said. "So it gets tough, but you try to do the best you can."

Zim still trying to work through throwing problems

WSH@DET: Zimmerman makes a leaping catch at third

WASHINGTON -- Ryan Zimmerman has made 17 errors at third base this season, most of which are the result of a surgically repaired AC joint in his right shoulder. He said in early June that the shoulder is not 100 percent and that 2013 would basically be a rehab year.

Manager Davey Johnson was asked Tuesday if Zimmerman should switch from third base to first.

"If that doesn't get better, then obviously it's not a good spot for him to be in," Johnson said. "But at one time he had a cannon, and we're all waiting for him to come back. I still think it's more mental, not just trusting it and cutting it loose. I see his work and he throws the ball pretty good, and then you see him having to play real shallow and almost cheating in, so it's not all together there yet is what I'm saying."

Johnson thought that Zimmerman would need until June to adjust his mechanics, but the Nationals' skipper is surprised that the issues still haven't been worked out.

"I knew it was going to take until June, but obviously it's taken longer," Johnson said. "It's more about him, if you see him throw early, he throws deeper and throws the ball on line. I don't know if it's physical or mental."

Worth noting

• Johnson made a few changes to the lineup on Tuesday, shifting Zimmerman into the No. 2 spot for the first time in the third baseman's career. When asked for an explanation of the changes, Johnson shrugged.

"It's just something. I don't know," he said. "I'm just throwing things up against the wall, and that one stuck."

• Johnson said Tuesday that Ohlendorf's right shoulder is "feeling better." The right-hander will throw on flat ground on Wednesday, then throw a bullpen session a few days later and go on a Minor League rehab stint a few days after that.

• Before Tuesday's game, shortstop Ian Desmond was named the team's recipient of the Heart and Hustle Award. The award was presented by Jim Hannan, the chairman of the Major League Baseball Players Alumni Association and a former pitcher for the Washington Senators, to recognize Desmond's passion and work ethic on and off the field.

At the end of the season, alumni and active players will vote among the 30 team winners. A final winner will be announced on Nov. 19 in New York.