Adam LaRoche’s first-inning, two-run shot off the façade of the upper deck in right field gives the Nats all the offense they would need Wednesday night at Nationals Park. (Jim Lo Scalzo/EPA)

The past two nights had left the Washington Nationals downcast, but even when they operate at less than full capability, they do not remain low for long. Their starting rotation will not let them. The Nationals have yet to launch, to pile up enough victories in succession to leave the reeling Atlanta Braves in their wake. But they also have yet to plummet.

The collective strength of their starters in general — and the individual performance of Doug Fister in particular — has made them immune from the force currently undoing Atlanta. The Nationals don’t do losing streaks.

The Nationals snuffed out another losing streak before it formed Wednesday night with a 7-1 victory at Nationals Park over the New York Mets. Fister improved his record to 11-3 and lowered his ERA to 2.49 after he allowed no earned runs in 71 / 3 innings. He won for the seventh time after a Nationals loss. He received a standing ovation as he walked off the field and tipped his cap as he reached the dugout. He operated, like always, with the efficiency of a NASCAR pit crew.

“It’s no coincidence, I feel like, a lot of runs get scored when Doug pitches,” first baseman Adam LaRoche said. “He’s pitching to contact. Guys are on their toes. There’s a lot of action. He gets you back in the dugout quick. It seems like when he’s pitching, we’re out there for 30 minutes on defense and spend two hours in the dugout.”

The Nationals’ power-deficient offense drilled three homers. Two came from LaRoche, who slumped through July. Danny Espinosa added a three-run blow in the sixth. With Fister on the mound, LaRoche’s first-inning, two-run shot off the facade of the upper deck in right field gave the Nationals all they needed. Espinosa’s liner into the first row in left ended the competitive portion of the night.

Bryce Harper is bewildered by a strike call in the sixth inning that Harper believed to be ball four. (Jonathan Newton/The Washington Post)

Bryce Harper ripped a line-drive single and drew a walk, putting his much-discussed slump on pause. And Denard Span smoked a single to left in the third, extending his on-base streak to 32 games.

The Nationals nudged their lead in the National League East to a season-high four games over the Braves, who lost their eighth in a row Wednesday in Seattle. The Nationals have suffered no such affliction. They lost Monday and Tuesday but have not lost more than four straight all season. They have endured only four losing streaks of three games or more and none since June 25.

“Quality starting pitching will do that,” Manager Matt Williams said. “They’ve got the ability to stop a skid if we get into one.”

The Nationals’ starter has thrown at least seven innings in 19 of their past 30 games. Their 3.17 ERA entering Wednesday ranked fourth in the majors. Their combined 15.7 wins above replacement, per, ranked first. Losing streaks don’t form when your starter gives you a chance to win every night.

“Our job is to go out there and get seven innings done,” Fister said. “If we can get more than that, great. But we got to get seven innings.”

Fister carried a 3-0 lead with him to start the second inning Wednesday and dared the Mets to hit solo home runs. He faced 27 batters and went to a three-ball count one only once, against Juan Lagares, who struck out swinging at a 3-2, 90-mph sinker in the fifth. Fister allowed no extra-base hits, and he erased two singles with an immediate double play.

“It’s certainly nice to get that” lead, Fister said. “I don’t take that for granted at all. But it’s still a 0-0 ballgame in my head. I still got to go up there, put up a zero and get our guys back in hitting. That’s not something that makes me relax or do anything extra. It’s still the same game.”

The Post Sports Live crew discusses which baseball teams improved and which teams missed out at the MLB trade deadline. (Post Sports Live/The Washington Post)

Since the all-star break, the Nationals had hit six home runs in 692 plate appearances. Collectively, they had been pounding pitches over the fence at about the same rate as San Diego Padres shortstop Everth Cabrera. LaRoche seemed an unlikely candidate to snap the power drain. Since July 1, he had managed only one homer.

LaRoche’s numbers cratered in July, when he hit .159. Against Mets starter Jonathon Niese, LaRoche worked himself into a 2-1 count. Niese fired a cutter, and LaRoche crushed it to right field, giving the Nationals a 3-0 lead. In the first six games of August, LaRoche is 8 for 21 with four walks, two homers and two doubles.

“It’s nice to see them go in the seats and not to the warning track or just foul,” LaRoche said. “I feel like I was kind of snake-bit last month. I never really felt lost at the plate, which I have plenty of times in the past. I felt like I was right there. I figured it was a matter of time. Hopefully this is the start of something.”

With his first homer since May 12, Espinosa continued his excellence when hitting from the right side against left-handed pitchers. He is slugging .518 from the right side this season compared with .295 from the left side.

“Consistency,” Espinosa said. “I go up there, and I do the same thing. I go up there with the same stance. I know what I want to do. I know what I can do. Left-handed, I’ve been searching as far as comfort in my stance. Right-handed, I’ve been the same guy.”

For the first time Wednesday, Espinosa, a switch hitter, publicly entertained the idea of batting only from the right side, but he said it would have to be an offseason project.

LaRoche smashed another homer, a solo shot to right, in the eighth inning. Fister watched from the dugout. Shortly thereafter, the Nationals would line up and shake hands, another losing streak avoided, another chance to launch.

“It’s been slow and steady this whole year,” LaRoche said. “No real big droughts and no long win streaks. Now would be a good time to take off.”

Nationals note: Jayson Werth exited after the sixth inning with soreness in his right shoulder and neck. He took a “funky” swing last week and tweaked his shoulder, Williams said, but the Nationals believe the injury is “nothing serious.” Werth could play in Thursday’s 12:35 p.m. matinee.