Ian Desmond is greeted at the top step of the dugout by Manager Davey Johnson and Denard Span after hitting a two-run home run in the fourth inning. (John Bazemore/ASSOCIATED PRESS)

The Washington Nationals’ season has begun with a rocky start of inconsistent play, a losing record in the first month and the team bending from the weight of lofty expectations. On Wednesday, they sent their best pitcher to the mound against their toughest division opponent, and Jordan Zimmermann delivered a 2-0 gem to beat Atlanta, a masterpiece that snapped a three-game losing streak but was still overshadowed by an injury scare to Bryce Harper that had the potential to be a devastating blow to an already listing offense.

Zimmermann (5-1) fired eight spotless innings, extending his scoreless streak to 18 and lowering his ERA to 1.64. Ian Desmond provided the only offense a beleaguered lineup needed, a two-run home run in the fourth inning. But perhaps the best news the Nationals received came after the final out, when Manager Davey Johnson said Harper was day to day after he was pulled from the game following a sixth-inning at-bat that left him grimacing in pain.

Harper, the reigning National League rookie of the year who was off to an even better start in his second season, departed after a check swing against Braves left-handed starter Paul Maholm. Harper grounded out to end the at-bat on the next pitch, but something looked awry. After talking with head trainer Lee Kuntz and Johnson on the bench in the dugout, Harper was pulled.

This week alone, the Nationals endured scares to two of their prized cornerstone players. Stephen Strasburg dealt with right forearm irritation during Monday’s start against the Braves, at first described as the potentially more troublesome forearm tightness. Two days later, the most powerful and consistent bat in their struggling lineup exited after a swing that at first appeared to be a worrisome oblique injury. “That’s never a good thing to see,” catcher Kurt Suzuki said.

The injury, however, turned out to be the remnants of a bad bruise from Tuesday’s game.

The Post’s Jonathan Forsythe says we should be worried about Stephen Strasburg’s pitching arm after his start on Monday night. (Post Sports Live)

“He didn’t want to come out of the ballgame but I saw him grimacing and I was concerned about him playing,” Johnson said. “We couldn’t take a chance on it. He could pull a lat or something and he could be out for a long time.”

Harper hurt himself on a play in the fifth inning of the previous game when he hit the right field wall trying to pull back a home run hit by Tim Hudson. Harper’s left side scraped against the wall and it still bothered it during Wednesday’s game. When he held back his swing, all weight was pushed onto the left side of his body.

“Got me to the point where I couldn’t breathe real quick and had to catch my breath,” Harper said. “It didn’t feel very good.”

Harper then hit the Maholm offering toward first baseman Freddie Freeman, who made a slick play to nab the ball. Harper, however, trotted down the line only halfway. Harper didn’t want to exit the game, but Johnson sent Roger Bernadina out to play right field in the bottom of the inning.

Following the game, Johnson was relieved. Harper, who iced the bruise, wasn’t given any tests and was set to receive medication. Harper will be re-evaluated Thursday.

“If I can play [Thursday], I’m gonna play,” Harper said. “If they put me in the lineup, I’m gonna play. I can play with pain and I can tolerate pain, so hopefully there’s nothing that can keep me out of that lineup. . . . Hopefully I can come in and feel like a million bucks and play.”

Lost in the concern over Harper was the dominance of Zimmermann, who picked up a depleted offense by allowing just two base runners. The Nationals were already without Jayson Werth, who fouled a ball off his left ankle in Monday’s game and hasn’t played since, and Ryan Zimmerman, the team’s cleanup hitter, who has been on the disabled list since April 18. Johnson sat struggling second baseman Danny Espinosa, and played Steve Lombardozzi, hoping to jump-start the offense.

The Nats’ offense only produced three hits (one more than the Braves), but Zimmermann made sure Desmond’s blast would stand. He pitched to contact, throwing 107 pitches, 72 for strikes, and struck out eight. He filled the strike zone with all four of his pitches — even a few change-ups — and walked none.

“I’m very proud, happy with the way the season has started,” Zimmermann said. “I’ve got to give a lot of credit to the defense, they’ve been doing great. I haven’t been striking many guys out.”

“I thought he was among the elites last year,” Johnson added. “We didn’t get him much run support last year. But he pitched awfully well and he’s taken it up another notch this year.”

Zimmermann followed up the finest pitching performance of his career in the previous start, a one-hit shutout against the Cincinnati Reds in Washington, with yet another impressive outing. He powered the Nationals to their first win in six tries over the Braves. Johnson didn’t want to pull Zimmermann after eight innings but he wanted closer Rafael Soriano, who hadn’t pitched in four days, to start the ninth. Soriano pitched a perfect inning to notch his eighth save.

“You want to be a stopper, that’s for sure,” Zimmermann said. “We had been struggling the last couple games, and I wanted to go out there and go as deep as I can and try to get a win and stop this losing streak.”

The Nationals could breathe easier Wednesday night. They have finally beaten their heated division foe. Harper escaped a serious injury and Zimmermann snapped their losing streak.