Nationals shortstop Ian Desmond fails to prevent an RBI single by Adam Jones in the eighth inning. (John McDonnell/The Washington Post)

The Washington Nationals had shown signs of late that they might snap out of their season-long inconsistency. Their impotent offense put 42 runners on base in the previous three games, and though only a third of them scored, it was improvement. Perhaps a meeting with their regional American League foe, the Baltimore Orioles, on Monday and in front of a sellout crowd at Nationals Park would extend the revival.

Instead, the 41,260 in attendance watched as Nationals silencer Jason Hammel yet again neutralized a lackluster lineup and Gio Gonzalez stumbled against a hot-hitting offense in Washington’s 6-2 loss. Excitement for the yearly interleague meeting of the nearby teams coursed through the stadium even late in an already determined game. But late in the second month of the season, the underlying frustration over the Nationals’ sleepy offense remained.

“There’s a lot of season left, but we need to get going,” third baseman Ryan Zimmerman said.

After a string of improved starts, Gonzalez surrended four runs in 52 / 3 innings, three of them coming in a laborious fourth inning. Hammel, on the other hand, entered Monday’s game with a 5.37 ERA and had yet to complete the seventh inning this season but held the Nationals to two runs over eight innings in 107 pitches. Without the injured Bryce Harper, their best hitter, the Nationals sprinkled eight hits but left six men on base.

Hammel, a former member of the Colorado Rockies, improved to 6-0 with a 3.14 ERA against the Nationals, the most wins without a loss by any active pitcher against Washington. His hard sinkers filled the strike zone at 93 to 94 mph and invited contact. The Nationals failed to get into the Orioles’ struggling and injured bullpen.

“That’s been kind of our M.O.,” Manager Davey Johnson said. “We were showing signs of coming out of it.”

The Nationals needed a strong pitching performance against the second-best hitting team in baseball to overcome their own shortcomings. Gonzalez allowed three base runners over the first three innings. His pitches, according to catcher Kurt Suzuki, were moving a lot. But a few too many pitches were up in the strike zone. And the mashing Orioles smacked them around.

“It seems like I was still getting myself out of situations and then I’d put myself in situations,” Gonzalez said.

With a 1-0 lead in the fourth inning, Gonzalez stumbled. He walked slugger Chris Davis to lead off the inning, the third of four walks he issued. Then came the assembly line of Orioles hitters.

Matt Wieters singled, and then Steve Pearce lifted a ball to left. Left fielder Tyler Moore, a first baseman converted to an outfielder, caught the ball and fired a strike to Zimmerman. Davis beat the tag by inches, and Gonzalez faced a one-out mess. With an American League team in a National League stadium, Gonzalez desperately needed to get the eighth-place hitter out. If he could, he would have two outs and the pitcher coming to bat. He couldn’t.

Yamaico Navarro fouled off three fastballs and held off on two curveballs in the dirt. With a full count, Gonzalez fired a 94-mph fastball in on Navarro’s hands. Navarro blooped it into left field to tie the game. Hammel’s subsequent sacrifice bunt moved the two runners into scoring position, setting up Nick Markakis’s two-run single. The Orioles took a 3-1 lead they wouldn’t relinquish.

“It wasn’t hit soft enough for us to make a play, and he just lined it right where it needed to be,” Gonzalez said. “That’s basically it. It was just one bad inning, and after that if I could’ve turned that page, I’d still be pitching the game.”

Gonzalez gave the Nationals another 12 / 3 innings before yielding to the Nationals’ maligned bullpen. Craig Stammen and Henry Rodriguez each allowed one run to put the game further out of reach. Even as Rodriguez pitched in a four-run game in the eighth, fans remained interested. Opposing fans dueled with cheers and boos. The stands blended both Nationals red and white and Orioles orange and black. Applause for the Nationals was met with “Let’s go O’s!” The excitement from last season, the first year since baseball returned to Washington in 2005 that both teams reached the playoffs, was apparent.

The Nationals put the leadoff batter on base against Hammel four times but pushed only two across home plate. Gonzalez led off the third inning with a double but advanced no farther than third base. Roger Bernadina, struggling with a .113 average and filling in for Harper, doubled to start the seventh inning but stood there for the next three outs.

The Nationals’ offense has been hampered by injuries this season and a scuffling bench. Harper missed Monday’s game and is expected to miss at least one more with a swollen and bruised knee. Starting right fielder Jayson Werth and catcher Wilson Ramos are on the disabled list. Danny Espinosa has sat for the past four games because of a fractured right wrist. The absences were apparent.

“When you’re struggling a little bit offensively and you take out one of your better hitters it doesn’t help,” Johnson said of Harper. “But certainly we have the talent and we’re certainly capable. We’re just not quite getting there.”

The Nationals, facing a 4-1 deficit after five innings, seemed poised to rally in the sixth. Denard Span led off with a triple to right field. With one out, Zimmerman singled softly to right to plate Span. Adam LaRoche lifted a flyball to center for the second out. Ian Desmond kept the inning alive with a single to center. But Moore added to the offensive misery by striking out on a 95-mph outside fastball.

“We just haven’t been able to consistently, up and down the lineup, put together good at-bats day in and day out,” Zimmerman said. “When you can’t do that you don’t score runs. We’ve just got to keep working, keep getting better each day.”