Ryan Zimmerman, left, and Michael Morse both hit home runs for the Nationals. (Dave Einsel/AP)

Sunday night, as the Washington Nationals’ team plane flew here from Atlanta, Manager Davey Johnson walked next to Jason Marquis, Monday night’s starter. The mental carryover from Sunday’s walk-off defeat had started to wear off. The physical toll had not. Their relievers combined for 123 pitches over 62 / 3 innings, bringing the bullpen’s three-day totals to 241 and 14. “Shambles,” was Johnson’s concisely grim summation.

“I just need nine out of you,” Johnson told Marquis on the plane. “That’s all I need.” Marquis just grinned.

Under those desperate circumstances Monday night, and in a 5-2 victory over the Houston Astros before 28,975, Marquis delivered precisely what the Nationals needed. For just one night, the hero was Ryan Zimmerman, who delivered the tying home run in the seventh and the go-ahead single in the ninth. But Marquis’s eight-inning, two-run performance carried just as much weight going forward. By stabilizing a bullpen that badly needed a night off, Marquis helped the Nationals return to .500 at 48-48 and enhanced their chances for the next two days.

“It’s big,” Zimmerman said. “Coming from that tough game yesterday, for him to be able to go that long was huge for us.”

Any of the scouts in attendance fixing their eyes and radar guns on Marquis, a veteran starter whom contenders have called the Nationals about trading for by the July 31 deadline, could only have upgraded their opinion. He struck out nine for the fourth time in his career, allowing six hits and a walk. It came against the team with the worst record — now 31-65 — in the majors, but Marquis’s performance was mostly dominant nonetheless.

Pitcher Jason Marquis of the Washington Nationals wipes his chin with his jersey in the second inning. (Thomas B. Shea/Getty Images)

Marquis, one day after a sprained ankle knocked Tom Gorzelanny out after two innings, understood the circumstances. Three Nationals relievers — Tyler Clippard, Ryan Mattheus and Henry Rodriguez — were completely unavailable. Johnson hoped a fourth, Sean Burnett, could also get another day’s rest.

“If you’re a baseball player, you’re part of a team, you should be aware of everybody’s situation,” Marquis said. “As a part of the team, you’ve got to realize those situations.”

Marquis threw 112 pitches, and no Nationals reliever even threw a warmup pitch until the ninth, when Drew Storen entered to preserve a three-run lead and cinched his 25th save by striking out the last three hitters he faced.

“It was a nice change of pace for us,” Storen said. “The less that phone rings, the better. That’s going to come up huge the next couple days for us, too.”

Marquis dueled 20-year-old rookie Jordan Lyles to a draw until the ninth inning, when the Nationals exploded for three runs. The Nationals managed only two hits in the first eight innings against Lyles, a right-hander, but both were home runs. Michael Morse hit the first, which was last seen traveling upward as it crossed high over the left field fence in the fifth inning; it might still be going. Zimmerman hit the second, and it landed in the first row beyond the right field fence. What Zimmerman’s homer lacked in majesty it made up for in significance — it tied the score at 2 in the seventh inning.

The Nationals entered the ninth tied, the same scenario they faced Sunday in Atlanta. Then, they lost on a walk-off hit. Monday, Roger Bernadina led off with a single to right field. Danny Espinosa dropped down a sacrifice bunt, a curious tactic, perhaps, given his team-leading 17 homers.

“I’m not a big proponent of the sacrifice,” Johnson said. “But I got three hot hitters coming up behind him. There was no question in my mind I was going to bunt him.”

Washington's Michael Morse passes Houston Astros shortstop Angel Sanchez, left, after hitting a solo home run. (Dave Einsel/Associated Press)

It worked exactly as Johnson imagined: Bernadina stood on second base with Zimmerman batting, drawing second baseman Jeff Keppinger a step toward the bag to hold him on. Zimmerman poked a chopper through the right side, just past Keppinger’s dive, a hit that allowed Bernadina to race home easily.

The Nationals blew the game open from there. Morse singled and Jayson Werth walked to load the bases. Laynce Nix chopped a ball over the head of drawn-in first baseman Carlos Lee, scoring another two runs.

The Nationals didn’t produce their first hit until the fifth, when Morse just about turned a baseball into a puff of vapor. Lyles made his first real mistake of the night by greeting Morse with a hanging curveball. Morse blasted it high down the left field line, over the seats. It landed somewhere around the train tracks below the wall of windows. Morse’s 16th homer gave the Nationals a 1-0 lead.

The Astros estimated it traveled 385 feet. “They got some bad technical help there,” Johnson said. “Because that thing was 450 if it was an inch. That was a bomb.”

Given a 1-0 lead, Marquis temporarily came unglued to start the fifth inning. He gave up a double to Jason Michaels and a double by Carlos Corporan down the first base line that scored Michaels. Neither team had sent a base runner past second base in the first four innings, and now both had scored a run in the fifth.

The Astros seized the lead in the sixth, after Marquis yielded another RBI double. With two outs and Sanchez on first, Lee hooked a double down the left field line and into the corner. Nix dug the ball out with his bare hand, but his throw forced cutoff man Ian Desmond to leap to his right, giving him no chance to attempt a relay throw home. Sanchez slid in without resistance, and the Astros led 2-1.

Marquis stabilized the game from there and Zimmerman, as he has done so many times, played the hero. When the Nationals gathered in the clubhouse Monday night, they were surely grateful for Zimmerman’s decisive hits. When their bullpen is stocked with fresh arms Tuesday, they will be thankful for Marquis’s performance.

“He got me eight,” Johnson said afterward, grinning. “He pitched a great game.”