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WASHINGTON -- Stephen Strasburg's warmup session in the bullpen had lasted about a half-dozen tosses when Nationals pitching coach Steve McCatty approached the star rookie with a simple question.

"I just said, 'Well, how're you feeling?' He said, 'I feel stiff. My shoulder's stiff,' " McCatty recounted.

"I said, 'How bad?' He said, 'It's just stiff, but I can get loose.' I said, 'Uh, no.' And that was it," McCatty continued.

With Strasburg suddenly scratched with what was later diagnosed as shoulder inflammation, reliever Miguel Batista was pressed into making his first start in nearly two years -- and the 39-year-old journeyman turned out to be rather Strasburglike on Tuesday night.

Batista allowed only three singles through five scoreless innings, two throwing errors hurt Atlanta starter Tommy Hanson, and the last-place Nationals beat the NL East-leading Braves 3-0.

Batista (1-2) hadn't started a major league game since Aug. 25, 2008, for Seattle, and he didn't know he would be taking the mound until minutes before the scheduled first pitch. That's because Strasburg was supposed to making the 10th appearance of his much-hyped career.

But the No. 1 overall pick in the 2009 amateur draft, who signed a record $15.1 million contract, had problems warming up.

"Stephen was having trouble getting loose in the bullpen, and so I pulled the plug on it," Nationals general manager Mike Rizzo said, adding that he considered it a "precautionary move."

"There's no shooting pains or anything like that in his shoulder or elbow," Rizzo said.

Strasburg was sent for medical tests -- an MRI and X-ray showed no structural damage, Rizzo said -- and was listed as day to day.

"For him not to pitch was a little disappointing, but I applaud what the Nationals did, because that's their franchise for the next 15 years, and if he wakes up with a hangnail, I'm pulling him out," Braves third baseman Chipper Jones said. "I want to protect my investment, protect that arm for the next 20 years. Because as he goes, they're going to go."

Strasburg's teammates were a little worried when they learned he was not going to play.

"It lets a little air out of your chest," outfielder Nyjer Morgan said.

When the announced sellout crowd of 40,043 was told of the change in pitchers from Strasburg to Batista, fans responded with boos. They booed some more when a longer explanation was delivered before the third inning.

"Imagine if you go there to see Miss Universe," Batista said, "and you end up having Miss Iowa."

But Batista was quite good, striking out six and walking one.

"I just tried to give the people what they came to see," he said with a smile. "They came to see a 20-year-old; they end up having an almost 40-year-old."

Relievers Sean Burnett, Drew Storen and Matt Capps completed the shutout, combining to retire Atlanta's final 10 batters. Capps threw a perfect ninth for his 25th save in 29 chances.

Hanson (8-7) went six innings, giving up three runs -- only one earned -- and six hits. He had eight strikeouts without a walk.

Morgan led off the game with a single, then stole second and third. Catcher Brian McCann's attempt to throw out Morgan at third base went into left field for a throwing error and allowed a run to score.

"When he goes, we go. When he's stealing bases, it's like mayhem out there," said Ian Desmond, who delivered a two-run single after Jones' throwing error in the second. "He has the ability to change the game."

Game notes

Nationals RHP Tyler Walker has a torn labrum in his pitching shoulder and expects to have season-ending surgery Friday. He'll be examined by noted surgeon James Andrews on Thursday. Walker, a reliever who went on the DL last month, had a torn labrum repaired in October 2000. "Once every 10 years," Walker said. That's not too bad. Go in and rotate the tires." He went 1-0 with a 3.57 ERA in 24 appearances this season. ... Before the game, a hearing was held in Braves LHP Jonny Venters' appeal of his four-game suspension for throwing consecutive pitches at Milwaukee's Prince Fielder on July 17. Venters pitched two hitless innings on Tuesday.