Atlanta Braves' B.J. Upton (2), Reed Johnson (7), and Andrelton Simmons (19) celebrate after playing the Washington Nationals in a baseball game, Sunday, June 2, 2013, in Atlanta. Atlanta won 6-3.

ATLANTA - Fredi Gonzalez doesn't want to discuss the NL East standings.

In fact, one mention of the Braves' big lead in the division made Atlanta's manager groan and complain "I don't even want to talk about that. It's June 2."

Ramiro Pena and B.J. Upton hit home runs, Paul Maholm won his third straight decision and Atlanta beat the Washington Nationals 6-3 on Sunday to stretch their lead in the NL East.

The Braves won two of three from the Nationals and lead Washington by 6.5 games - the biggest advantage for any first-place team in the majors. Atlanta is 15-6 against NL East teams, including 7-3 against the Nationals.

"It's big," said Upton of winning the series against the Nationals. "We know they're a team that's going to be around all year. They have a good ballclub. It's good to win games against a team like that."

The Nationals (28-29) fell below .500 for the first time since they were 13-14 on April 30. It may seem early in the season to Atlanta's Gonzalez, but Washington's Adam LaRoche said it's late for the Nationals to be scuffling around .500.

"We deserve to be where we're at right now," LaRoche said. "We've played like crap. And we're still not in awful shape.

"That only goes so far. We're pretty deep into the season, so we've got to get it going or we won't be there at the end. I don't sense any panic, anybody stressing over it, but it'd be nice to pick it up."

Washington manager Davey Johnson said the team's sagging offense could get a lift as outfielder Jayson Werth is expected to come off the 15-day disabled list for Tuesday's start of a home series against the Mets.

"There's still plenty of time," Johnson said. "We can right the ship and get things going in the right direction. We've still got plenty of time.

"The offense is just sputtering a little bit. It'll be good to get Jayson back. Our guys are certainly capable. They've just got to start doing it. That's all. It's that simple."

Ian Desmond hit a homer for Washington in the sixth inning to cut Atlanta's lead to 4-3. Freddie Freeman answered with a bases-loaded, two-run double in the bottom of the inning.

Paul Maholm (7-4) allowed three runs, two earned, on five hits in six innings. Craig Kimbrel pitched a perfect ninth for his 17th save.

Washington rookie Nathan Karns (0-1) gave up four runs, three earned, on seven hits in 4 2-3 innings. Karns allowed two homers. He has given up four homers in his two starts.

Upton, who had the game-winning hit in the Braves' 2-1 win over the Nationals in 10 innings on Saturday night, hit a second-inning homer off Karns to give Atlanta a 3-2 lead.

The two-game surge was much-needed for Upton, who has RBIs in back-to-back games for only the second time this season.

"Good for him," Gonzalez said. "His at-bats keep getting better and better and better. That's the B.J. Upton that we want to see. It's good that he's coming along.

"Hopefully he'll run off 10 or 12 games like this."

The Braves led 2-0 before Karns recorded an out. Ryan Zimmerman's 10th error on a wild throw to first allowed Andrelton Simmons to reach base. Pena hit Karns' next pitch about five rows deep into the right-field seats for his third homer.

Washington tied the game with two runs in the second. LaRoche doubled and moved to third on Ian Desmond's bunt single. Tyler Moore's single to left field drove in LaRoche. With two outs, Karns hit a grounder to Freeman at first base. Maholm dropped Freeman's toss to first base for an error as Desmond scored.

Karns was pulled after giving up a single to Justin Upton and a two-out walk to Evan Gattis in the fifth. Brian McCann's single off Zack Duke drove in Upton for a 4-2 lead.

Desmond's seventh homer cut the lead to 4-3 in the sixth before Freeman's bases-loaded double off Duke in the bottom of the inning pushed the lead to three runs.

Freeman's drive hit the yellow line on the top of the left-field wall. Three umpires left the field for a video review to confirm the on-field ruling the hit was a double.

"I blame it on the wind," Freeman said with a smile. "It's a big park. C'mon guys, move the fences in."

Washington right-hander Erik Davis, recalled from Triple-A Syracuse on Saturday, pitched 1 2-3 perfect innings in his major league debut.

NOTES: The Braves held out slumping right fielder Jason Heyward, who struck out in each of his three at-bats on Saturday night, leaving his batting average at .142. Justin Upton moved to right field and Gattis started in left field. ... B.J. Upton made back-to-back starts for the first time since May 21-22. ... The Braves open a three-game series against Pittsburgh on Monday night as RHP Kris Medlen, still looking for his second win, faces RHP A.J. Burnett. The Nationals, off on Monday, return home to open a series against the Mets on Tuesday night when RHP Jordan Zimmermann faces RHP Jeremy Hefner.