The win gives first-place Washington a six-game lead in the NL East, while Atlanta lost its third in a row.
Ian Desmond led off the 13th with an infield single off Cristhian Martinez (5-3) before Espinosa tried to bunt and hit into a forceout. Kurt Suzuki then hit a slow roller for an infield hit, allowing Espinosa to take third.
With the infield in, Tracy hit a ball to Braves second baseman Dan Uggla, who appeared confused and instead of either trying to get Espinosa at the plate or attempting to turn a double play, he fumbled it, and Espinosa scored the game-winner.
Uggla was initially given an error before it was changed to a single for Tracy.
Craig Stammen (6-1), Washington’s eighth pitcher and final remaining reliever, pitched two hitless innings for the win.
In the first, Martin Prado, who had three hits, doubled with one out against Jordan Zimmermann. He scored on Jason Heyward’s single.
The Nationals scored four runs in the first off Tim Hudson. Jayson Werth led off with a double and scored on Bryce Harper’s single. Ryan Zimmerman then singled, and both runners moved up when Michael Morse lined a ball that ricocheted off Hudson’s right hand. Harper came home on Adam LaRoche’s infield out and Desmond hit a two-run home run to left – his 18th of the season.
In the fourth, Chipper Jones walked, Uggla doubled, and with one out Paul Janish lined to Espinosa at second. He couldn’t handle it, and Jones scored on the single.
Heyward’s two-run homer in the fifth tied the score at 4. It was his 21st of the season.
Zimmermann pitched five innings, equaling his shortest outing of the season. He allowed four runs on four hits, walking two and striking out two.
Hudson, who hasn’t lost since the Nationals beat him July 1, allowed four runs and eight hits. He walked two and had his six-game winning streak broken.
NOTES: The Braves signed 1B Lyle Overbay to a minor league contract. Overbay, released by Arizona on Aug. 5, will report to Triple-A Gwinnett on Thursday. ... RHP Lucas Giolito, the Nationals’ first-round draft choice, has been shut down and will have his right elbow examined in Los Angeles by Dr. Lewis Yocum. “The worst-case scenario is Tommy John surgery, and we’ll see if that’s where we’re headed,” Washington general manager Mike Rizzo said. ... The game’s start was delayed by rain for 56 minutes. ... On Tuesday, Atlanta’s Paul Maholm (11-7, 4.39 ERA) will face Stephen Strasburg (14-5, 2.91).