ATLANTA -- Washington slugger Bryce Harper owns Atlanta pitcher Julio Teheran and the same could be said about the Nationals against the Braves.

Harper smashed a grand slam in the second inning after a solo homer in the first off Teheran and finished 4-for-4 with an intentional walk as the Nationals won 14-4 on Wednesday night. It was their 31st victory in the past 40 games against Atlanta.

"It was just a bad day," Teheran said. "I didn't have it at all. Obviously, it was one guy that hurt me the most. He's hit me really good. He's one of the best hitters. But it's a long season."

Harper, who is batting .404 with six homers and 18 RBIs this season, has driven in 17 runs against Teheran while going 15-for-33 with seven homers against the right-hander.

"I'm not looking at who I'm facing or what he's going to do to me or anything like that," Harper said. "I just try to see a pitch and drive it the best I can. ... I respect all pitchers."

Joe Ross, recalled from Triple-A Syracuse, got plenty of support from Harper and Ryan Zimmerman in Washington's 20-hit outburst. Ross went seven innings to win his season debut.

Ross (1-0) retired 14 of the last 15 batters he faced. The right-hander allowed six hits and three runs while striking out seven and walking one.

"I like how he settled down and started getting the ball down, because early they were hitting some balls hard off him," Nationals manager Dusty Baker said. "He started picking up his tempo (and) finished strong."

Zimmerman made it a rout with a grand slam off reliever Ian Krol in a five-run eighth. It was the first time the Nationals hit two slams in a game since Josh Willingham did it in 2009 at Milwaukee.

Freddie Freeman hit his sixth homer of the season in the third inning to set the Atlanta record of reaching base in 12 consecutive plate appearances.

Freeman, who had walked his first time up, grounded out in the sixth to end the streak before delivering an RBI single in the eighth.

Teheran (1-1) came in with a 0.95 ERA for his first three starts, but he allowed seven runs in four innings against the Nationals (9-5). The Braves (6-8) have lost eight straight games that Teheran started against Washington.

Harper picked on a first-pitch fastball down the middle of the plate for his first-inning homer, to right-center field. He then deposited a hanging 1-0 slider from Teheran over the center-field fence in Washington's five-run second that erased a 2-1 deficit.

"He's real hot right now, obviously," Braves manager Brian Snitker said. "Julio was a little off and he got hurt."

Adam Eaton, who has reached base in all 11 games he has started for the Nationals, had an RBI single to tie the score before Harper connected for the grand slam.

Nick Markakis and Brandon Phillips had RBI singles in the first inning and Freeman, who had scored after a walk earlier, homered over the center-field fence off Ross on a 1-0 fastball in the third.

The Nationals got that run back in the fourth, though, as Teheran added to his rough outing with a run-scoring wild pitch.

NOTES: It took RHP Blake Treinen, who had a 7.11 ERA in eight games, less than three weeks to lose his closer role with the Nationals. Manager Dusty Baker said RHP Shawn Kelley and RHP Koda Glover will share the ninth inning, with Treinen returning to a setup role. ... Washington LF Jayson Werth left the game during a third-inning at-bat when he tweaked his groin checking a swing. ... The Nationals placed LHP Sammy Solis on the 10-day disabled list with elbow inflammation to make room for RHP Joe Ross, who was recalled from Triple-A Syracuse to start against the Braves. ... Atlanta LF Matt Kemp (hamstring) was 1-for-3 with a sacrifice fly for Triple-A Gwinnett on Wednesday and is expected to return from the disabled list for the series finale against the Nationals on Thursday. ... Washington SS Trae Turner (hamstring) played in an extended spring training game and will be activated during the weekend series in New York against the Mets. ... RHP Stephen Strasburg (1-0, 3.00 ERA) will pitch on Thursday for the Nationals, with RHP R.A. Dickey (1-1, 3.86) starting for the Braves.