Chris Johnson singled with two outs off left-hander Jerry Blevins (1-1), and Schafer pinch-ran. With a 2-2 count, Schafer ran on the pitch and Upton dropped a single in front of Bryce Harper.
Schafer already was rounding third when Harper bobbled the ball. No error was charged.
Luis Avilan (2-1) pitched around two walks, one intentional, in the 10th.
Upton hit a solo home run in the eighth off Tyler Clippard that tied the score 6-all, his third homer in two games. Atlanta’s Ramiro Pena and Washington’s Ryan Zimmerman hit three-run drives — Zimmerman following a throwing error by Dan Uggla on a routine grounder to second.
Denard Span’s single off David Carpenter drove in Harper in the eighth to put the Nationals ahead 6-5.
Atlanta burst ahead with a four-run second against Tanner Roark, who allowed five runs and five hits in 4 2/3 innings.
Julio Teheran could hold the lead, giving up five runs — two earned — and 10 hits in six innings. Ian Desmond had a run-scoring single in the fourth, when the Nationals left the bases loaded.
Washington manager Matt Williams used his appeal in the seventh inning when Adam LaRoche was called out at the plate when trying to score on Jordan Walden’s wild pitch with Harper batting. The pitch bounced away from Gattis toward the Nationals dugout. Gattis looked behind him before finally spotting the ball and throwing to Walden, who made the tag. Plate umpire Adrian Johnson’s call was confirmed in the video review.
Braves closer Craig Kimbrel struck out Jayson Werth, Adam LaRoche and Zimmerman in the ninth. Washington’s Drew Storen fanned Pena, Ryan Doumit and Jason Heyward in the bottom of the inning.
Pena made his second straight start for shortstop Andrelton Simmons, who jammed his right wrist in a home-plate collision on Wednesday night. Manager Fredi Gonzalez said he wanted to give Simmons one more day “to make sure he’s fine.”
“I don’t want something small to become something big,” Gonzalez said.
NOTES: Nationals RHP Doug Fister (DL, back muscle) threw 35 pitches in the bullpen before the game. “He was really impressive,” Williams said. “The ball had good life.” Williams said Fister will go on a minor league injury rehabiliation assignment after he increases his pitch count in bullpen sessions. ... Roark hit Freeman, Uggla and Upton with pitches. ... Simmons was presented his 2013 Gold Glove and Platinum Glove Awards by Rawlings in a pregame ceremony. ... The 10 hits allowed matched Teheran’s career high, also against the Nationals on April 29 last year. ... Braves LHP Alex Wood is to face Nationals RHP Taylor Jordan in the second game of the series tonight.