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The Washington Nationals will be likely be without superstar Bryce Harper on Monday when they begin the Beltway Series against the Baltimore Orioles at Nationals Park.

The first two games of this set will be contested in Washington, D.C., with the final two games being played in Baltimore's Camden Yards.

Harper has been battling a sore knee since crashing into the right-field wall at Dodger Stadium back on May 13. He appeared to aggravate the injury in the Nationals' 6-1 win on Sunday against Philadelphia and had to leave the game for a pinch-runner in the seventh inning.

"I have to deal with the pain and try to (stay) in there every day. We'll see what happens," Harper said.

While Harper was dealing with his knee pain, Stephen Strasburg took care of business on the mound, as he scattered five hits and one run over eight strong innings. He also struck out a season-high nine batters without allowing a walk.

At one point, Strasburg sat down 10 straight and 15 out of 16 batters.

Steve Lombardozzi went 1-for-4 with a two-RBI double and a run scored in the win, while Adam LaRoche went 2-for-4 with two runs scored for the Nationals, who have won three of four after a four-game losing streak.

"Just trying to get it going a little," Nationals third baseman Ryan Zimmerman said of the series win. "We haven't strung too long of a streak together this year."

Hoping to keep that momentum rolling on Monday will be lefty Gio Gonzalez, who is 3-2 with a 3.66 ERA. Gonzalez did not receive a decision on Wednesday in San Francisco, but pitched well, as he held the defending champs to a run and four hits in 7 1/3 innings of his team's 2-1 win.

Gonzalez has allowed just five earned runs in four starts this season, but has just one win in that stretch.

"It's just a matter of time until the guys start swinging the bats, until everything starts clicking," Gonzalez said. "I think that sometimes it gets to a point where you just remember that all this is a team thing. Individual things are nice, but at the end of the day, we're all looking at one thing: how to win the game. So when I got out there and pitch, I try to keep my team in the game as long as possible and give them a chance to win."

Gonzalez has faced the Orioles five times and is 1-2 with a 3.26 ERA.

Baltimore, meanwhile, will counter with righty Jason Hammel, who has won five of his last six decisions. Hammel beat the New York Yankees on Wednesday, limiting them to a pair of runs and six hits in 6 2/3 innings, as he improved to 6-2 to go along with a 5.37 ERA.

Hammel's roll should continue on Monday, as he is a perfect 5-0 lifetime versus the Nationals with a 3.30 ERA in seven starts.

Baltimore was denied a series win on Sunday against Toronto, as closer Jim Johnson blew his fourth save in five chances and allowed four runs in the ninth inning in a 6-5 loss at Rogers Centre.

"We should be getting on the plane with three wins here, but I can't hang my head too long," said Johnson, who has given up 12 earned runs in his last five save opportunities.

Baltimore took four of six games from the Nats last season.