WASHINGTON -- The Washington Nationals were not looking ahead. The Atlanta Braves do not have much to look forward to.

The suddenly surging Nationals gathered momentum heading into a huge series Monday against the New York Mets by completing a four-game sweep with an 8-4 triumph on Sunday over the hapless Braves, who are mired in a run of failure.

It would have been understandable for the Nationals to let their minds drift to a potential division-deciding three-game set with the Mets, but they took care of business against the Braves, improving to 10-0 against Atlanta at Nationals Park this season and moving to four games behind New York for the NL East lead.

Washington has now won five straight games and completed its first four-game sweep of the season.

"We've just been playing good baseball," Nationals outfielder Bryce Harper said. "We just have to keep doing what we're doing, keep having fun, keep having good at-bats and just be the team we are. We're a great team. We have a lot of fun. We just have to worry about what we're doing and that's all we can ask for at the end of the day."

The Nationals took advantage of the beleaguered Braves rotation once again, tagging Atlanta starter Manny Banuelos for seven runs in the first three innings and cruising from there.

Nationals left fielder Jayson Werth had the big blow, with a three-run homer in a five-run second inning. Harper hit his 34th homer, his third in as many days, and second baseman Anthony Rendon added a solo shot as Washington rolled up 36 runs in the four-game series.

"It was a good series," manager Matt Williams said. "The guys swung the bats well, pitched well. So we got these. Now we've got a lot of work to do."

The Braves, who on July 8 were 42-42, have seen their season devolve into a nightmarish series of new lows. Their 12th straight defeat is their longest run of losing since a 12-game skid that encompassed the end of the 1987 season and the start of the 1988 campaign. Atlanta has dropped 19 of its last 20 contests and 34 of its last 43.

Sunday's loss also marked the first time since 1990 that the Braves went winless at an opponent's ballpark in a season series of nine or more games.

"I've never seen anything like this," Braves catcher A.J. Pierzynski said. "Just keep battling and come tomorrow and try to win."

Washington starter Joe Ross seemed in line to pick up his sixth victory of the season, but as the rookie reaches new heights in innings pitched, it appears he may be running out of gas. Ross lasted just 4 1/3 innings, giving up four runs on five hits while walking three and striking out none. Five Nationals relievers, led by Felipe Rivero (2-1), held Atlanta to just two hits the rest of the way.

Williams was non-committal when asked about Ross' role in the rotation going forward.

"That's a big discussion for us," Williams said. "We have to understand where he's at, the territory he's in and what options we have going forward."

Left-fielder Nick Swisher drove in two runs and scored another, while Pierzynski added an RBI single, moving him into sole possession of 10th place on the all-time catcher hit list at 1,970. But the Braves also committed three errors, two on back-to-back plays in the third inning.

"Today we played sloppy," Braves manager Fredi Gonzalez said. "We didn't play good baseball, but we stayed after it. It's tough. It really is tough."

NOTES: Both teams had late scratches, as Atlanta sat 3B Hector Olivera due to a bruised foot, replacing him with Adonis Garcia. Washington 1B Ryan Zimmerman received a late rest day, with Tyler Moore stepping in to replace him. ... Nationals OF Bryce Harper crossed the 100-run mark Saturday and needs just 17 more RBIs to become the first Washington player to tally 100 walks, 100 runs and 100 RBIs. ... The Nationals now lead the all-time series 100-99. ... Atlanta opens up a series against the Phillies on Monday, with RHP Williams Perez starting against Philadelphia RHP Aaron Harang. The Nationals start a three-game set with the Mets on Monday, with RHP Max Scherzer facing Mets LHP Jon Niese.