Atlanta’s Matt Diaz is nonplussed after lining out in the second inning. With the win, Washington stretches its lead in the NL East to 4 games over the Mets and 4 1 / 2 games over the Braves. (John Amis/Associated Press)

For his first 20 games this season, Michael Morse looked little like himself. His timing was off. He wasn’t consistent. The man who hit 31 home runs last season for the Washington Nationals had only one. The oblique injury that cost him 50 games had thrown everything out of whack and it showed when he returned.

“Right off the bat, you’re trying to go out there and do some impossible stuff,” he said.

Earlier this week, Morse went to Colorado and clobbered the ball. Friday night in Atlanta, Morse proved his suddenly torrid hitting was the result of his growing comfort at the plate, not just the thin air of the Rocky Mountains.

He finished 4 for 4, including a solo home run in the eighth inning that was the decisive run in the Nationals’ 5-4 win over the Braves.

While Morse saved the game, it was left-handed starter Ross Detwiler who saved his team’s arms.

After a series of shootouts against the Rockies, the weary bullpen needed a strong outing from Detwiler, who was making his second start since returning to the starting rotation.

He would have to be stretched out and, if possible, pitch deeper into the game than he had in a month.

“We needed it so bad I can’t even tell you,” Manager Davey Johnson said.

When the left-hander was moved into the bullpen in late May, something clicked: He found a renewed aggressiveness.

Against the Braves, he displayed it. Detwiler breezed through the first four innings, allowing only one hit. He allowed no runs until the seventh, extending his scoreless streak to 182 / 3 innings. Working out of the bullpen had forced him to pitch faster and more efficiently.

Detwiler pitched into a jam with a 4-0 lead in the fifth inning but Johnson left him in. Detwiler loaded the bases by allowing a double, hitting a batter and committing an error on a soft groundball in front of him. But he induced a flyout to deep right field from Andrelton Simmons for the third out.

Detwiler faced a similar situation in the seventh.

Again, Johnson left him in to mop up the mess and rest the bullpen. Detwiler hit Freddie Freeman with a pitch. He then failed to field a sacrifice bunt by Jack Wilson. A balk moved everyone over a base.

Detwiler then allowed a RBI single to pinch-hitter Martin Prado, the Braves’ best hitter. Out came pitching coach Steve McCatty to the mount to talk with Detwiler. To grow as a starter, Detwiler needed to clean up this mess, too.

Michael Bourn lifted a sacrifice fly to left field to trim the deficit to 4-2. Again Simmons came to the plate in a crucial spot against Detwiler. On his 93rd pitch of the night, Detwiler hung a curveball over the plate and Simmons crushed it to left field for a game-tying, two-run home run. Within a span of six batters, Detwiler lost his streak and blew the lead. But the 62 / 3 innings he chewed put the Nationals in a spot they needed: handing the ball to setup man Sean Burnett and closer Tyler Clippard.

“Det gave us just what the doctor ordered,” Johnson said. “It’s a shame that he made really one bad pitch and it cost him the ballgame.”

Added Detwiler: “We had an extra-inning game yesterday and those guys need their rest.”

Detwiler had been staked to a lead by a sputtering offense that was jump-started to life with 33 runs in the final three games of their series in the glorious altitudes of the Rocky Mountains. While what happened at Coors Field is commonplace there, it gave slumping hitters such as Morse and Ryan Zimmerman a chance to shed the mental aspect of their slumps, Johnson said.

Zimmerman, who only a week ago was contemplating a second stint on the disabled list for his ailing right shoulder, has been on a tear since receiving a cortisone shot. He went 2 for 5 Friday to improve to 11 for 28 with two home runs and eight RBI since the shot.

Morse also rediscovered his touch at the plate in Denver and has raised his batting average from .217 to .294 by batting 13 for 23 in the past five games.

“I’m starting to have better at-bats,” Morse said. “I’m starting to see, recognize pitches. It comes with, basically, at-bats. Seeing the ball more, just being up at the plate, watching a pitcher.”

Morse, who scored the game’s opening run in the second on an RBI single by Detwiler, would be the center of another productive inning when the Braves’ infield struggled in the third. Adam LaRoche reached on an error by Wilson.

Morse singled to the left side, a line drive off the glove of third baseman Chipper Jones.

A throwing error by Simmons on the play put LaRoche and Morse in scoring position. Ian Desmond then bolstered his all-star candidacy when he singled in two runs for a 3-0 lead.

Catcher Jesus Flores added a solo home run in the fourth inning to give the Nationals a 4-0 lead — one that seemed comfortable the way Detwiler was pitching.

Johnson nearly held Morse out of Friday’s game because of the tightness in his right hamstring. He made Morse promise not to run hard and to tell him if it flared up again.

Before the eighth inning, Morse told Johnson the hamstring was tightening up and told him to ready a pinch-runner just in case.

There was no need. Morse’s powerful swing sent a pitch from Chad Durbin into the right field seats. As he walked into the dugout, Johnson congratulated Morse.

“I told him, ‘That’s the way to keep me from running for you,’ ” Johnson said.