Buck finished 3-for-4 and scored three runs while Stefen Romero had a pinch- hit, three-run home run for the Mariners, winners of their last four contests.
Seattle's bullpen shut down the Braves after a rocky start from Erasmo Ramirez, with four pitchers allowing just two hits and a pair of walks in six scoreless innings. Dominic Leone (2-0) fanned four batters in two innings of relief to earn the win.
Fernando Rodney pitched a 1-2-3 ninth inning to secure the win and collect his 15th save of the season.
Evan Gattis crushed a three-run homer and B.J. Upton collected two hits, one being a solo shot, and scored a pair of runs for the Braves, who had their three-game winning streak snapped.
Alex Wood (5-6) served up the go-ahead home run to absorb the loss.