Center fielder Denard Span doffs his cap to the crowd after his game-saving catch of Hunter Pence’s drive in the ninth inning clinched the Nationals’ fifth straight victory. (Jonathan Newton/The Washington Post)

The ball screamed off Hunter Pence’s bat. The game hung in the balance, and one thing raced through Denard Span’s mind. “Oh, [shoot],” Span thought. Typically precise with his reads in center field, Span had taken a false step toward the infield. Pence’s drive hissed toward the gap. If it dropped, the Washington Nationals would lose their lead in the ninth inning. If Span caught it, the game was over. He put his head down and sprinted.

“I didn’t think he was going to get to it,” Manager Davey Johnson said.

Span chewed up ground for three steps and peeked at the sky. It was then he realized he had a chance. Seconds later, after a fully extended dive and a snow-cone snare, the crowd gasped and teammates rushed toward him to celebrate Wednesday night’s 6-5 victory over the San Francisco Giants. First, Span held his glove in the air to show Nationals Park the ball. Then he stood up and smiled.

“It saved the game,” right fielder Jayson Werth said.

In his first year in Washington, Span has stunned teammates with his speed and grace in center field, traits that have redeemed his inconsistent offensive output. But he hadn’t made a catch with the importance or degree of difficulty of this one.

“I take pride in my defense,” Span said. “Would I like to be hitting .400? Of course. But I love the feeling of taking a hit from somebody or robbing a home run or robbing an extra-base hit. There’s no better feeling than being able to do that, especially like tonight.”

Span’s best moment so far as a National reinforced a sudden truism: The Nationals don’t lose. One week prior to Wednesday night, the Nationals hobbled off the field with the Atlanta Braves’ tire marks on their backs and their season in a million little pieces. Trampled in their home stadium, having sunk to the lowest point of a dismal year, the Nationals approached the grim prospect of irrelevance.

“Maybe we just said, ‘Screw it,’ ” Werth said. “We just got our [butts] kicked. What do we got to lose? It was definitely a flip that was switched. Hopefully it was the right one.”

Would that crew recognize itself just seven days later? The Nationals have not lost since the Braves eliminated any realistic hope of winning the National League East. They still stand one victory away from .500, but they matched their season-high five-game winning streak.

“This game, it kind of beats you down so bad at times,” reliever Tyler Clippard said. “I feel like we hit rock bottom. . . . We did lose three to the Braves. But it let us take a step back and be like, ‘All right guys, let’s just play baseball and see what happens.’ That’s what we’re doing right now. And it’s a lot more fun that way.”

In their latest win, the Nationals took a 6-1 lead against right-hander Tim Lincecum and held on. Ian Desmond continued his torment of Lincecum with a 448-foot blast to left center, the longest home run hit this season at Nationals Park, which made him 10 for 12 in his career against Lincecum. “When I see him on the mound, I still think that he’s one of the best in the game,” Desmond said. “The numbers may not say so, but I kind of turn it up against him.”

A five-run fourth inning hinged on Anthony Rendon’s two-run, bases-loaded double. Clippard bailed out Ryan Mattheus, whose disastrous relief appearance in the eighth shrunk the Nationals’ lead from four to two. Jordan Zimmermann allowed one run over seven innings for his 14th win, Rafael Soriano recorded his 31st save thanks to Span’s catch.

A day after a breezy, 1-2-3 ninth, Soriano invited disaster. Pinch hitter Hector Sanchez led off with a single. His pinch runner eventually scored on Brandon Belt’s two-out single. Buster Posey kept the inning alive with a single to center. Up came Pence.

Span stationed himself a few steps toward right field, playing Pence the other way. Pence blasted a drive to left-center. In the Nationals’ clubhouse, Clippard and Zimmermann sat next to each other with ice on their shoulders, watching the game on television. The camera angle switched from the plate to the outfield and revealed where Span had started the play.

“We were like, ‘Oh, God,’ ” Clippard said.

“I didn’t think there was any way he was going to get there,” Belt said.

On the field, the Nationals never worried. They have been trained to trust in Span. “The guy can really go get the baseball,” Werth said. “Underrated, you know.”

Span, so fast Florida once recruited him to play defensive back, outran the ball. Span prides himself on never diving for balls, but this time he had no choice. He extended himself and slid on his back to the edge of the warning track. The ball thudded into his glove.

At shortstop, Desmond thought back to a recent play when an out popped out of Span’s glove. This time, white poked out of his mitt, but it stayed.

“Once my hand hit the ground, it tried to come out,” Span said. “But I wasn’t letting it go.”

Pence did not even see Span dive. He had been sprinting with his head down, hoping only that Posey, a slow runner, would be able to score from first on his double.

“The crowd noise made me look up,” Pence said. “I was in shock.”

Left fielder Bryce Harper shoved Span in the chest, fired up. Other teammates gave him fist pounds and high-fives. Span is hitting .262 with a .314 on-base percentage, both of which would constitute new career lows. Johnson recently dropped him from leadoff to seventh in the order. But his defense has been as good as the Nationals hoped when they dealt top pitching prospect Alex Meyer to the Minnesota Twins for him.

“You know what? That’s been the main thing that’s kept me going,” Span said. “ . . . We’ve been battling all year. I’ve been battling all year.”

Span has not quit, and neither have the Nationals. They have turned their season around against two teams, the Phillies and Giants, who look upon any problems the Nationals may have possess with envy. And they remain 81 / 2 games behind the Cincinnati Reds, who have kept their grip on the second wild card with seven wins in eight games.

The Nationals, though, are done worrying. They are ready to put their head down and see what happens.