ATLANTA (AP) -- Jace Peterson didn't know if he'd be able stay in the game after catching a ball and slamming into the center-field wall in the third inning.
Instead, he toughed it out, moved to second base in the ninth and used his bat to win the game one inning later.
"I got a little bit of a bruise on the face," Peterson said. "But other than that, everything feels good."
Peterson hit a tiebreaking homer in the 10th inning off Shawn Kelley and the Atlanta Braves took advantage of five Washington errors to beat the Nationals 7-6 on Sunday.
Rain delayed the game 1 hour, 4 minutes in the bottom of the eighth.
Kelley (1-2) hung his head and walked toward the dugout as soon as Peterson made contact with his seventh homer. Kelley gave up one hit and one run in two-thirds of an inning.
"We played a sloppy game," Washington manager Dusty Baker said. "We'd have been lucky to win that game with five errors."
Jose Ramirez (1-0) faced four batters in the 10th to earn the win.
Four Nationals errors led to runs for the Braves.
Nick Markakis cut the lead to 4-2 in the third with a two-run double and took third on shortstop Danny Espinosa's errant relay throw. Markakis made it 4-3 when center fielder Trea Turner caught a popup and was charged with a throwing error after dropping the ball as he transferred it to his right hand.
Anthony Recker scored from third in the sixth to cut the lead to 6-4 when second baseman Daniel Murphy threw errantly to first.
In the eighth, Matt Kemp's 25th homer cut the lead to 6-5. Reliever Yusmeiro Petit had a throwing miscue that advanced Jeff Francoeur to third. Francoeur made it 6-6 on a double-play grounder.
The Nationals went ahead 4-0 in third on Murphy's RBI forceout and Bryce Harper's 22nd homer, a three-run shot deep into the right-field seats. Chris Heisey put Washington up 6-3 in the sixth with his eighth homer, a two-run shot.
Peterson, making his first career start in center field, slammed his face and shoulder into the wall after making a twisting catch of Heisey's liner to end the third.
He fell to the warning track, stayed down for a couple of minutes and was escorted by a trainer to the dugout.
"I got the wind knocked out of me," Peterson said. "I couldn't breathe. That was really it."
Kelley hung a slider that Peterson hit into the right-field seats.
"I was totally confident walking him when (the count) got to 3-2, so I wasn't going to give him anything good to hit," Kelley said. "But I left slider right there in the middle of the plate."
Washington starter Gio Gonzalez allowed six hits, three walks and four runs - three earned - in 5 2/3 innings. He struck out eight.
Braves starter Joel De La Cruz allowed seven hits, six runs, two walks and four strikeouts in his 5 2/3 innings.
Washington is 25-7 against Atlanta since the start of 2015. The Braves are 19-44 at home. They had lost seven straight overall.
In his fourth career game, Braves SS Dansby Swanson, the No. 1 overall draft pick of 2015, went 0 for 4 with one walk and one run scored while hitting in the leadoff spot for the first time. Swanson went 4 for 12 in the No. 8 spot.
Braves 1B Freddie Freeman had a cortisone shot in the middle finger of his right hand after Saturday's game and didn't play. The finger has been bothering him since spring training. Freeman had cortisone shot during the All-Star break, too, and said he'll try to be in the lineup Monday at Arizona. ... Espinosa was hit by a pitch to load the bases in the third. He's the Nationals' career leader in getting hit by a pitch and has been hit 19 times this year, second-most in the NL.
Braves RHP Tyrell Jenkins was optioned to Triple-A Gwinnett. The rookie, acquired in the Nov. 2014 trade involving Jason Heyward and Shelby Miller, is 2-3 with a 6.30 ERA in eight starts. ... RHP John Gant was called up from Gwinnett.
Nationals: RHP Stephen Strasburg (15-4) is 1-0 with a 2.25 ERA in two career starts against Baltimore.
Braves: RHP Mike Foltynewicz (6-5) is 0-1 with a 6.23 ERA in three career starts against Arizona.