WASHINGTON -- Bryce Harper had a two-run double down the left field line off Eric O'Flaherty with two outs in the eighth as the Washington Nationals beat the Atlanta Braves 2-1 on Tuesday. The hit by Harper bounced off the glove of a diving Jeff Francoeur, who almost made a brilliant catch near the stands.

The Braves are now 0-7 this season and have lost their last 12 games at Nationals Park. Washington improved to 5-1 and is 25-9 against Atlanta since June 21, 2014.

The winning pitcher was Blake Treinen (2-0) while Jim Johnson (0-2) was tagged with the loss. Johnson gave up a one-hit single to Stephen Drew and then walked Anthony Rendon with two outs before O'Flaherty came in to face Harper in the eighth.

Felipe Rivero came on in the ninth with two outs and allowed an RBI single by Kelly Johnson before getting rookie Mallex Smith for the final out on strikes.

Washington starter Gio Gonzalez gave up just three hits and one walk in six innings while fanning four on 95 pitches. Home plate umpire Dan Iassogna had a strike zone that seemed to favor the hurlers on a chilly, windy night.

Jhoulys Chacin of the Braves allowed no runs and five hits in six innings with eight strikeouts in his first appearance of the season. He was around the strike zone all night as he threw just 69 pitches -- 52 for strikes.

Atlanta's Gordon Beckham (two hits) had a two-out double in the seventh off reliever Shawn Kelley, who retired pinch-hitter Jace Peterson to end the threat. The Nationals also escaped damage in the eighth as Treinen got Francoeur to ground into a double play to end the inning.

Adonis Garcia also had two hits for the Braves, and Daniel Murphy had two hits for the Nationals.

Gonzalez last faced big league hitters 16 days ago, in spring training. He was also pitching as a father for the first time in a regular-season game, as his girlfriend had a boy in March.

Chacin made his debut for the Braves after he went 2-1 with a 3.38 ERA in five games, with four starts, last season for the Arizona Diamondbacks.

NOTES: Braves 3B Adonis Garcia, who started and batted cleanup, turned 31 on Tuesday. ... Before the game, the Braves selected the contract of RHP Jhoulys Chacin from Triple-A Gwinnett, and they optioned RHP Joel De La Cruz to Gwinnett. De La Cruz, who was called up Monday when RHP Daniel Winkler went on the disabled list, did not get into a game with Atlanta. To clear a spot on the 40-man roster, the Braves transferred LHP Jesse Biddle (Tommy John surgery in October) from the 15-day disabled list to the 60-day DL. ... Nationals now have 12 wins in a row at home over the Braves. ... Washington RHP Stephen Strasburg (1-0, 1.50 ERA) faces Atlanta RHP Matt Wisler (0-0, 5.40) on Wednesday. ... The Braves began the season 0-6 for the first time since 1988, when they started 0-10.