The Nationals are dazed after being swept by the Braves at home. (Jonathan Newton/The Washington Post)

As the ball hissed off Justin Upton’s bat and rattled around the left field corner in the eighth inning Wednesday night, Nationals Park lapsed into a demented time warp: Close your eyes, peel away the expectations, and rushing back came 2010 or some other misbegotten season before it. Fans of the visiting team rose and cheered. Home fans skulked out of the stadium. Another game slipped away from the Washington Nationals and the manager’s grip loosened in a season going nowhere.

The Atlanta Braves snuffed out any realistic hope the Nationals could defend their National League East title with a merciless three-game sweep that culminated with a 6-3 victory and a whiff of resignation in the Nationals’ clubhouse.

“It’s getting to a point where we’re just not winning games,” said right fielder Jayson Werth, who went 2 for 3 with a walk and a two-run homer in the fourth inning. “You hate to accept losing at any point. But the losses are definitely piling up.”

Having gone 6-13 since the all-star break, the Nationals sit a season-worst six games below .500, 15½ games behind the Braves and nine games behind the Cincinnati Reds in the race for the second National League wild-card spot.

The Braves went ahead for good on a three-run, two-out rally in the eighth, which came against Ryan Mattheus and Ian Krol as Tyler Clippard sat idle in the bullpen. Manager Davey Johnson’s decision to keep his best reliever shelved added to a long day and a hard night. Johnson hobbled into his postgame news conference and announced he had thrown out his back in the afternoon.

The Post Sports Live crew debates whether Mike Rizzo deserved a promotion from Nationals General Manager to President of Baseball Operations. (The Washington Post)

“That’s how this year’s going,” he said.

Johnson went on to say Jordan Zimmermann had been limited to a four-inning, 88-pitch start in part because the neck stiffness he had dealt with earlier in the season had returned. When Zimmermann heard Johnson’s diagnosis, he pursed his lips and shook his head.

“That’s news to me,” Zimmermann said.

In the seventh inning, cameras caught Johnson and Bryce Harper shouting in the Nationals’ dugout. Harper had led off the bottom of the seventh with a flyball to left field, and then he trotted to first base.

“Yeah, I went over,” Johnson said. “I was concerned about his leg bothering him because he didn’t round the base. That was all that was about.”

Johnson added that Harper told him he “messed up” and didn’t want to leave the game. Harper said the conversation was not as heated as it seemed on television.

“He was checking out my leg, seeing how I felt,” Harper said. “I told him I felt fine and I didn’t want him to take me out of the game.”

Afterward, in an emptied Nationals clubhouse, Werth walked out of the trainer’s room and sat at his locker to face a waiting group of reporters. He had recently found notes he had written to himself before he signed a seven-year deal in December 2010 with Washington, thoughts about potential teams.

“I was just kind of reading over the notes, and for the Nats one of the things said we would be good toward the end of my contract,” Werth said. “It kind of put things in perspective with the success last year and, really, where we’re at now with the guys. We’re still in the building-type phase. I know with all the expectations, it didn’t really seem like that but we’ve got a lot of young players. The direction’s still good. We’ve got a lot of young talent, and there’s a lot of things to look forward to here in Washington.”

A reporter pointed out to Werth that the story did not come off as a ringing endorsement of the Nationals’ chances to make something of this season.

“It’s not over, you know?” Werth said. “We’re not there yet. And even when you get to that point, it’s not like you’re going to give up. As long as there’s a pitcher on the mound and I’m in the lineup, I’m going to give it the best effort. Right now it’s just, it’s not lining up for us.”

Their finale against the Braves fell apart in the eighth, immediately after the Nationals had tied it at 3 on Ian Desmond’s RBI fielder’s choice. Clippard did not pitch Tuesday. But Johnson struck with Mattheus, who had recorded the final out of the seventh.

Mattheus retired the first two batters he faced, then threw Andrelton Simmons a slider. Simmons drilled a double to left-center. Pinch hitter Joey Terdoslavich walked. With two outs and Jason Heyward coming to the plate, both Krol and Clippard were warming up. Johnson chose Krol, he said, because Heyward was 5 for 8 in his career against Clippard.

Krol jumped ahead of Heyward with two strikes. He tried to finish Heyward off with a curveball, but the pitch caught too much of the plate. Heyward hooked it into right field, and Simmons sped home with the go-ahead run.

Up came Upton. In the seventh inning, the Braves’ best right-handed hitter had faced lefty Fernando Abad and drilled a go-ahead home run. Now, Johnson let Upton face another lefty in Krol. “I’m not going to bring [Clippard] in down a run,” Johnson said. Upton unloaded on an 0-1 change-up, belting a double to left field. Another two runs crossed, and the Braves’ fans filling the park erupted.

The two-run homer Werth punctuated with an exaggerated bat flip, and the two scoreless innings Tanner Roark provided in his major league debut had been made moot. The Nationals would load the bases and force closer Craig Kimbrel to throw 36 pitches in the ninth, a rally sparked by Harper’s double off a 3-2, 98-mph fastball. The rally died when Wilson Ramos smashed a line drive to right, right at Heyward.

The Nationals could not surmount the Braves, and the possibility of a season gone bust had nearly turned into a reality.