Bryce Harper mirrors the Nationals’ frustrations Thursday after striking out in the first inning. (Ricky Carioti/Washington Post)

Alone, in the quiet of a sullen clubhouse, Rafael Soriano pulled a crisp white shirt over his shoulders and tucked it into gray slacks. He wrapped a black tie around his neck. He pulled black leather loafers out of a black leather bag — big league all the way — and slipped them on his feet. He walked past a pack of reporters, promising to return. “Let me get my tie up, please,” Soriano said.

Teammates glanced toward the scrum of notebooks and cameras as Soriano explained the wrenching conclusion to the Washington Nationals’ 4-3 loss to the San Francisco Giants. The Nationals’ winning streak reached an abrupt end when Soriano, one strike from protecting a two-run lead and sealing the Nationals’ sixth consecutive victory, yielded a three-run, pinch-hit home run to Giants rookie Hector Sanchez in the top of the ninth.

Soriano focused not on the 3-2 pitch Sanchez crushed down the right field line and into the upper deck. He fumed about the 2-2 cutter Sanchez had looked at for ball three, a pitch Soriano believed had been tucked inside the upper edge of the strike zone.

“I think the game [should have been] over,” Soriano said. “That pitch, to me, I think it be a strike. I think that was when the game changed.”

The year already had sapped most of the resolve from the Nationals, and now they will find out how much they have left. Just as they climbed back to the edge of contention, a small milestone turned into a disaster before 36,719 stunned fans.

Just as the Nats hit their stride, they fell down a trap door.

“That one hurt,” Manager Davey Johnson said. “That one hurt.”

Rather than reach .500 for the first time since July 19, the Nationals packed for Atlanta trying to stomach a crushing loss, nine games back of the second wild-card spot. Soriano suffered his career-high fifth blown save, Dan Haren’s latest tremendous start went up in flames and the Nationals’ flickering hopes to make September matter dimmed a little more.

“It definitely hurts,” Haren said. “The mood kind of stinks right now in here.”

Johnson had wanted to avoid using his two best relievers, Tyler Clippard and Soriano, each for the third straight day. But the Nationals did not add to the three runs it scored in the third inning, and so Johnson summoned Clippard to handle the eighth.

Before the ninth inning, he had Craig Stammen warming up next to Soriano, hoping the Nationals would tack on insurance runs and make a save chance obsolete.

They did not, marooning 11 runners in the process, six coming as Giants Manager Bruce Bochy used intentional walks to twice make Haren hit with the bases loaded and two outs.

“Probably the bigger story is, we had a lot of runners on base and we didn’t push them across,” said shortstop Ian Desmond, who roped a two-run double in the third. “We had the starter out after 32 / 3 and we didn’t score after that. We’ve got to do a better job to push more runs across.”

And so, in jogged Soriano to face the heart of the Giants’ lineup. The night before, he had earned the save only because Denard Span had made a game-saving, diving catch. Soriano had already worked three consecutive days four times this season.

“That don’t be no excuse,” Soriano said. “In the past, I do it for four days in a row. I feel fine.”

Buster Posey hit a two-strike slider — “a hanger,” Johnson said — for a leadoff single. Soriano recorded the next two outs to bring up Roger Kieschnick, a 26-year-old who entered with 19 strikeouts in 38 big league at-bats and had two hits in his previous 20 at-bats.

Soriano worked a 3-2 count against Kieschnick, then walked him with a misfired fastball. The game remained alive.

“You’ve got to get him out,” Johnson said. “Can’t come close to walking, got to make him put it in play. That’s what hurt.”

Soriano agreed.

“Yeah, because how the guy be hitting right now — I see every time at-bat,” Soriano said. “I think that was when I lose that game.”

The walk brought Sanchez to the plate as a pinch hitter. Soriano quickly got ahead of him with two strikes. The crowd rose in anticipation. Soriano tried to get Sanchez to chase two fastballs, and he took both for balls.

The 2-2 pitch just missed — the crowd groaned. PITCHf/x technology that tracks pitch location deemed the pitch a strike, just inside the upper portion of the strike zone. Johnson, though, thought home plate umpire Jim Joyce had kept a consistent strike zone all day — generous low, stingy high.

“I think, to me, that would be the game right there,” Soriano said. “I don’t think it be a bad pitch at all.”

Agitated, Soriano tried to regroup. He tried to throw a cutter inside. The pitch zipped over the middle of the plate, up and out of the strike zone — “it was a ball,” catcher Kurt Suzuki said. But Sanchez swung, and he crushed it into the upper deck.

The Nationals could not put anyone on base in the bottom of the ninth, thanks largely to Brandon Crawford’s diving stab of Bryce Harper’s liner. Signed this winter to a two-year, $28 million deal, Soriano’s ERA rose to 3.40, and he has allowed 50 hits and 12 walks in 501 / 3 innings.

The ninth inning has become an adventure, but Johnson feels no ambiguity about who his closer is.

“He’s been very consistent,” Johnson said. “He’ll give up some hits, but he makes pitches when he has to.”

Afterward, Soriano singled out Haren as the teammate he felt worst for. Given a 3-0 lead in the second inning, Haren allowed one run over six innings on just three hits and two walks. He lowered his ERA in seven starts since returning from the disabled list to 2.30.

“I definitely didn’t have my best stuff, but I made it work,” Haren said.

Thursday afternoon, Soriano threw five pitches with two strikes in the ninth. Any of them could have ended the game. He had to make a pitch, and he did not. The sting of a sudden loss erased good vibes attached to the Nationals’ winning streak, and a disappointing season added a new layer of frustration.