Trailing 5-4 entering their final at-bat, the Marlins struck for a pair of runs and sent the National League wild card-leading Braves to their 10th loss in 15 games.
Atlanta saw its lead trimmed to 2 1/2 games over St. Louis, which beat Philadelphia Monday.
With Florida down to its last out off Braves closer Craig Kimbrel (4-3), Emilio Bonifacio singled and Infante followed by blasting a long homer into the left field stands, handing the Marlins a win in the opener of a three-game series.
Clay Hensley (6-6) earned the victory with two innings of scoreless relief for the Marlins, who blew a 4-1 lead late in the game thanks in part to Infante's fielding error.
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