Updated

On Sunday, the Nationals' offense showed rare scoring punch in victory over Philadelphia Phillies starter Cole Hamels, enough to imagine manager Davey Johnson ending his shaving boycott soon.

On Monday, Orioles hurler Jason Hammel stymied Washington's Bryce Harper-less lineup and likely kept Johnson's scraggly facial hair around a little longer. He says he won't shave it until the Nats' bats show satisfactory progress.

Hammel held the Nationals to two runs in his longest start of the season while Gio Gonzalez allowed four in shortest outing since April as the Nationals fell to the Baltimore Orioles 6-2.

The Nationals played without Harper, who has swelling in his left knee.

Harper's injury was aggravated in Sunday's 6-1 win over the Phillies and underwent an MRI. Team medical director Wiemi Douoguih said the outfielder has inflammation of the bursa sac in front of his knee, which he anticipates "clearing up in a couple of days." Harper underwent an MRI, which showed some soft tissue swelling, but no structural damage, Douoguih said.

Washington's lineup did little damage against Hammel (7-2), who spun another gem at Nationals Park while improving to 4-0 in Washington. The right-hander struck out eight without a walk and allowed eight hits in eight innings.

"He used both sides of the plate with his fastball and threw some pretty good breaking balls," Johnson said of the latest starting pitcher to silence his batters. "We just didn't get the big hit."

Hammel threw a third-strike fastball past Tyler Moore to end the sixth inning and strand the potential tying run. Washington went 2 for 11 with runners in scoring position.

That's been kind of our M.O.," said Johnson, who vowed last week not to shave until the bats came alive. He kept the beard even though Washington scored six runs Sunday and had won three of four games.

"Gio wouldn't let me," Johnson cracked pregame about why a razor had yet to touch his face. "But we're getting close."

Perhaps, but the Nationals scored two or fewer runs for the 25th time in 51 games.

In this case, that was certainly no enough. Nick Markakis and Yamaico Navarro each drove in two runs and the Orioles had 15 hits, including three from Manny Machado.

After allowing only five earned runs and posting a 3-1 record in his previous three starts, Gonzalez (3-3) gave up four runs and eight hits over 5 2-3 innings with four walks and three strikeouts.

The Orioles were scoreless until tallying three runs in the fourth off Gonzalez. Navarro's bloop RBI single tied the score at 1 and put runners on first and second with one out. After Hammel bunted, Markakis hit a two-out, two-run single.

"I was getting myself out of situations, but then I'd put myself in situations," Gonzalez said of his scattered performance.

Gonzalez, who went 21-8 last season, pitched into the seventh inning in all four starts since allowing five runs in four innings at Atlanta on April 30. After this setback, he dealt with postgame questions regarding consistency issues on the mound this season.

"Four starts in a row isn't consistent? Seems pretty consistent to me," Gonzalez said. "You're entitled to have a bad game once in a while. I'm not going to be perfect, but at the same time I was in the zone, I was attacking them. ... That's a good hitting team, got to give them their credit."

Machado hit his AL leading 23rd double, stole a base and scored a run. The 20-year-old has seven games with at least three hits since May 10.

Moore's RBI single in the second gave the Nationals a 1-0 lead and Denard Span scored in the sixth on Ryan Zimmerman's single after tripling off Hammel.

Matt Wieters hit a sacrifice fly in the fifth put Baltimore up 4-1.

The Nationals and Orioles play four straight games this week with Wednesday and Thursday's contests held in Baltimore.

NOTES: Before the game, the Nationals placed LHP Ross Detwiler on the 15-day disabled list with a right back muscle strain and recalled LHP Xavier Cedeno from Triple-A Syracuse. After the loss, Washington sent Cedeno back to Syracuse and called up RHP Nathan Karns from Double-A Harrisburg. Karns will start and make his major league debut on Tuesday against RHP Kevin Gausman (0-1), who will make his second career start for the Orioles. ... Douoguih provided updates on several injured Nationals including catcher Wilson Ramos. Out since May 16 with a left hamstring injury, Ramos will miss another four weeks. ... Danny Espinosa (fractured right wrist) missed his fourth straight game, but could return to the lineup on Wednesday if no additional swelling takes place after the second baseman took swings on Monday. ... Jayson Werth, out since May 2 with a right hamstring strain, could play in rehab games later this week and return to the Nationals active roster next week. ... Hitting coach Rick Eckstein served as first base coach with Tony Tarasco absent due to the birth of his child. ... RHP Yunesky Maya, designated for assignment by the Nationals on Saturday, cleared waivers and was outrighted to Triple-A Syracuse.