Adam Jones sat in front of his locker, a huge bag of ice wrapped around his right shoulder and a look of disgust planted on his face.

Although Jones homered Saturday, the Baltimore Orioles lost to the Washington Nationals 4-2 to fall a season-worst six games under .500 (31-37).

Baltimore has dropped six of seven, including the first two games of this interleague series against their nearby rivals. After wasting 18 hits Friday night, Baltimore stranded eight Saturday and went 2 for 7 with runners in scoring position.

"We just have to be able to get the big hit," Jones said. "We have to be able to get the runner in. That's what it is. It's not a lack of baserunners, it's not a lack of opportunities. It's just a lack of production."

Brian Matusz (1-2) absorbed his second straight loss and left in the sixth inning with cramping in his left hamstring.

Asked if he was concerned about missing his next start, Matusz said, "I would say no. I don't think it's a strain or anything like that. It's just a cramp."

With the score tied at 1, the Nationals went ahead for good in the sixth. Ryan Zimmerman hit a one-out double and Michael Morse followed with his 13th home run. Ivan Rodriguez added a two-out RBI double off reliever Clay Rapada, which irritated manager Buck Showalter because pitcher Jordan Zimmermann was on deck.

"We made a poor pitch on Pudge," Showalter said. "We shouldn't even be touching the strike zone with the pitcher on deck. That hurt us."

J.J. Hardy singled in a run in the seventh, but that's as close as the Orioles would come. Drew Storen worked a perfect ninth for his 17th save in 19 tries.

Matusz was making his fourth start since being activated from the disabled list on June 1 after missing two months with a strained muscle in his left side. In his previous appearance, he yielded four runs, five hits and four walks in 1 1-3 innings against the Tampa Bay Rays, who openly wondered whether the left-hander was at full strength.

Matusz pitched well for five innings against Washington but came unglued in the sixth. He was charged with four runs and six hits in 5 1-3 innings.

"It was a huge step forward from my last start. That's pretty evident," Matusz said.

Matusz wasn't the only Oriole forced out of the game with an injury. Luke Scott left in the fourth inning with back spasms.

"First swing of the day, slider inside, I got some spasms going on in my back," he said. "I just finished the at-bat, kept going, hoping that the pain would subside or loosen up. Then it just kept staying tight, especially when I breathe and take a deep breath. It was hard for me to move."

Scott did not expect to be sidelined for more than a day or two.

Washington has won eight in a row, its longest winning streak since an eight-game run from Aug. 2-9, 2009.

The game attracted a crowd of 36,614, the second-largest of the season at Nationals Park behind opening day. The teams drew 35,562 fans on Friday night.

Zimmermann (5-6) gave up two runs and eight hits in 6 1-3 innings to win a third consecutive decision. The right-hander has not allowed more than three runs in nine successive starts since April 26.

"The last couple starts have been good," he said. "This one, it was good, but I didn't have my best stuff."

Jones and Zimmerman both hit solo homers in the first. It was the 10th of the season for Jones and the second for Zimmerman, the first since his return from the disabled list after missing 58 games with a left abdominal tear.

Derrek Lee hit a one-out double in the Baltimore fourth and took third on a single by Felix Pie. Zimmermann then struck out Mark Reynolds and retired Robert Andino on a grounder.

Notes: LHP Tom Gorzellany will be activated on Sunday to start for Washington. He's been on the disabled list since May 23 with an inflamed left elbow. ... RHP Brad Bergesen, recalled from Triple-A Norfolk before the game, pitched two scoreless innings. ... Morse now has 42 RBIs, a new career high. He had 41 in 98 games last year.