Buck followed with a single to center for a 3-1 lead that chased Medlen. Lagares' flyout to right field added another run.
Medlen gave up four runs and seven hits in 5 1-3 innings. He dropped to 4-1 in 18 outings against New York.
"I've been making more mistakes than I have been in the past," Medlen said. "Like I say, I'm just trying to make the adjustments and fix it while I can."
NOTES: The Braves are 25-29 on the road. ... Mets RHP Jenrry Mejia will start the opener of a doubleheader in Washington on Friday. The 23-year-old Mejia had Tommy John surgery in June 2011. He made five September appearances last year, but has been on the DL since the end of spring training with elbow inflammation. Collins said: "We wanted him to understand — what he's hearing today about (Zack) Wheeler, (Matt) Harvey, was all about Jenrry Mejia three years ago in the same vain." ... Gonzalez was still gushing about Jason Heyward's game-ending diving catch Monday night, saying it might've been the best catch he's seen all season. ... It was "Star Wars" night at Citi Field. ... There was a sunshower before the game.