Gio Gonzalez walks to the dugout after being relieved in the sixth inning. (David Goldman/Associated Press)

The usual feeling Gio Gonzalez evokes when he pitches is joy. Sunday night, it was fatigue. The Atlanta Braves turned his bid to win 20 games into a shift on the assembly line. They spit on balls on the edge of the strike zone. They flicked and fouled away tough pitches. He threw his final pitches through persistent rain. His nationally televised showcase became a backbreaking slog, and the Washington Nationals headed home with a pennant race still on their hands.

The Braves swept the Nationals out of Turner Field with a 5-1 victory, knocking Gonzalez out after five grinding innings and punishing their sloppiness to seal the game. The Nationals could have virtually eliminated the Braves from the National League East race this weekend. Instead, their magic number to win the division remained 11 and their lead went from 81 / 2 games to 51 / 2 with 16 more to play.

It would still take a horrific collapse by the Nationals to lose the division. Even if the weekend breathed life back into the Braves, the Nationals focused on their standing rather than on the wasted weekend. Manager Davey Johnson ambled through the clubhouse as players packed for home, spitting one-liners and drawing laughter.

“We’re fine,” third baseman Ryan Zimmerman said. “We’ve put ourselves in a great position. We’ve played well all year, and we have two weeks left of playing baseball. Everything is right in front of us.”

With a chance to reverse momentum and state his case for a Cy Young Award, Gonzalez threw 110 pitches as he allowed two runs in five-plus innings on four hits and four walks. He limited damage and kept the Nationals in the game, but the Braves also wore him down enough to get to the Nationals’ bullpen in the sixth inning.

“I wasn’t pounding the strike zone,” Gonzalez said. “I was nipping the corners, trying to be too perfect. They’re scrappy. They’ll work a count.”

Left-handed pitchers have stymied the Braves most of this year; they entered Sunday 27-29 against them. Lately, though, they have managed to neutralize Gonzalez. In his last three starts against Atlanta, a possible playoff opponent, Gonzalez lasted five, five and 42 / 3 innings.

The Nationals brought the hottest offense in the National League here on Friday, and the Braves silenced it. The Nationals went scoreless at one point for a span of 12 innings, and they struck out 35 times in the three games while scoring six runs.

The Braves broke open Sunday’s game with three runs in the seventh inning, which they scored with only one hit. A leadoff walk, an error on Ryan Zimmerman and an RBI groundball scored the first run. The Nationals had given the Braves the game-winning run Saturday, and now they handed over an insurance run.

They were not done. Sean Burnett loaded the bases with an intentional walk of Chipper Jones and by hitting Freddie Freeman with a breaking ball. Dan Uggla provided the key blow, a two-run single to left field that gave Atlanta’s lights-out bullpen a four-run lead to protect.

The unsightly seventh inning defined the series. The Nationals walked 13 batters and hit two while committing three errors. In sum, they gifted the Braves 18 base runners in three games.

“We can’t do that,” Johnson said. “We’ve been pretty good all year.”

The Braves eroded Gonzalez’s stamina in the opening innings. Eight of the first 14 hitters Gonzalez faced took at least five pitches. Reed Johnson flied out on the 10th pitch of his first at-bat, and Uggla drew a nine-pitch walk in his. By the end of the second inning, Gonzalez had thrown 50 pitches.

Patient and disciplined, the Braves would not relent. Michael Bourn led off the third with an eight-pitch walk. He scooted to third on a hit-and-run single by Jason Heyward. With one out, Gonzalez faced a jam with runners on the corners.

Gonzalez needed an out. He put two quick strikes on Jones. Jones fouled off a fastball, took a curveball in the dirt and then flared another fastball foul down the right field line. Gonzalez fired a 92-mph fastball, the eighth pitch of the at-bat. Jones hammered to left-center field for an RBI single.

“They were working the count,” Gonzalez said. “They were making me work that strike zone. When I did come back, it was right where they wanted it. It’s kind of obvious what’s coming after you’re sitting 3-2.”

Freeman used up six more pitches before he drilled a sacrifice fly to left field, scoring Heyward and putting the Braves ahead, 2-0. Gonzalez escaped the inning without further damage, but he had thrown 83 pitches after only three innings.

After the third inning, veteran bench player Mark DeRosa sidled next to Gonzalez. “Hey, a little more confidence on the mound,” DeRosa told him. “We need that mound presence.”

Gonzalez felt as though a switch had been flipped. He retired the next six batters he faced, using up only 20 pitches to pitch through the fourth and fifth. In the dugout, Gonzalez found DeRosa and smiled. “Where were you in the first inning?” he said.

“The only thing that [stinks] is it started a little too late,” Gonzalez said.

Through it all, Gonzalez kept the Nationals in the game. After the fourth, Gonzalez found Johnson in the dugout.

“I’ll kill you if you take me out,” he said.

“I’m not,” Johnson replied. “You’re going to win this ballgame.”

The Nationals had done nothing against left-hander Mike Minor, but Bryce Harper lashed a ground-rule double over the left-center field wall to lead off the sixth. After two outs, the inning fell to Ian Desmond with Harper on third. He flared a 1-2 fastball into shallow center field. Of his 68 RBI this year, 30 have come with two outs. The most recent slashed the Nationals’ deficit to one.

The Nationals could not come any closer. They had to absorb news about Danny Espinosa, who on Monday will receive an MRI exam on his left shoulder and will miss at least the next three games. Johnson is worried about Espinosa, but not about his team’s position.

“I feel fine about where we’re at,” Johnson said.