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5/30/2013 11:45 P.M. ET

Tightness lingers for Werth on rehab assignment

BALTIMORE -- Nationals outfielder Jayson Werth has played nine innings in two nights on a rehab assignment with Class A Potomac, but manager Davey Johnson said that Werth still felt some tightness in his strained right hamstring.

Johnson added that there is no chance that Werth will join the team in Atlanta during its three-game series against the Braves.

"No. No possibility. Although, Jayson may say after today, 'I'm ready,'" Johnson said. "Just depends how much he puts into today and how he feels. Still worried about a little bit of tightness in there."

Werth started in right field for Potomac on Wednesday night and went 1-for-2 at the plate in three innings of action. On Thursday, he played six innings and went 2-for-3 with two singles.

Before Thursday night's game, Johnson said that the plan was for Werth to play five innings on Thursday, then seven and nine in his next two games. Werth was placed on the 15-day disabled list on May 11.

Harper eyes return in series opener in Atlanta

BALTIMORE -- Nationals outfielder Bryce Harper is aiming to return to the lineup Friday against Atlanta, manager Davey Johnson said before Thursday's game against the Orioles.

"I had a good talk with him yesterday," Johnson said from the visitors' dugout at Camden Yards. "He hit yesterday and he's going to try and do a little more today. He's shooting for tomorrow."

Harper has missed the past four games with bursitis in his left knee. He injured the knee on May 13, when he collided with the outfield wall at Dodger Stadium, and reinjured it Sunday after twice sliding head-first in the first inning.

Before Thursday's game, Harper played catch in left-center field and took batting practice with the Nationals' reserves. He hit three straight home runs in one stretch, and two of his batting-practice homers bounced through the right-field gates and onto Eutaw Street.

"I think it's lessened enough to where he feels a lot better about it," Johnson said about Harper's knee. "He says it doesn't bother him to hit, but we're not going to have a DH in Atlanta."

Potential changes could come to spark Nats

BALTIMORE -- The Nationals fell to .500 after a 2-0 loss at Camden Yards on Thursday night, and manager Davey Johnson said after the game that he will probably make some changes to the lineup.

"Well, I mean we need to get some guys back that are hurt and some of the young guys are struggling," he said. "We'll probably make some changes. But that's for another day."

One potential change could be the insertion of utility player Steve Lombardozzi into the starting lineup at second base. Danny Espinosa rested his fractured right wrist for five games, and Lombardozzi was 6-for-20 (.300) with two doubles and four RBIs as his replacement. The 24-year-old had three hits in two of his past seven starts.

When asked before Thursday's game if Lombardozzi could start at second base, even with a healthy Espinosa, Johnson was noncommittal.

"He's a heck of a player. He's played awfully well," Johnson said. "Again, Danny Espinosa is certainly capable of playing well, too. And I need them all playing well. So we'll see how it goes. See how he handles playing with a hand not 100 percent. And I'll make the decision then."

Johnson said that there was no swelling in Espinosa's wrist after his return to the Nationals' lineup on Wednesday. And after Thursday night's game, Espinosa said that the wrist "feels fine" and that he no longer feels it clicking during at-bats. He is 4-for-41 (.098) in his past 11 games and 1-for-7 since returning to the starting lineup.

Johnson also could insert utility player Jeff Kobernus, who only has one Major League at-bat, into the starting lineup at second base or either corner-outfield spot. Or, perhaps more likely, the Nationals' skipper could shuffle his batting order with hopes that the change will spark the offense.

"Frustration? Yeah, I'm sure there's some frustration. But what are you going to do? Are you going to flip things over and get mad every day?" Espinosa said of the Nationals' recent struggles. "That's not going to do anything. So I think as long as we go in prepared every day and get ready the way we know how to get ready, then it's going to start going our way."

Tom Schad is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.