Dan Uggla led off with a single up the middle off Arquimedes Caminero (0-1), and Gattis followed with a shot into the left-field seats for his fifth homer of the season — and first career walk-off homer.
Andrelton Simmons homered for the Braves, and Jason Heyward put Atlanta ahead 2-1 with a seventh-inning single off Mike Dunn. Anthony Varvaro (1-0) worked a scoreless inning for the win.
Julio Teheran turned in another stellar outing by Atlanta’s rotation, allowing only one run and five hits over seven innings. He actually lowered Atlanta’s starting ERA, already the best in the majors, from 1.54 to 1.52.
Garrett Jones homered leading off the second for Miami. The Marlins tied it in the ninth with Derek Dietrich’s run-scoring double off Craig Kimbrel.
After failing to get three outs in a non-save situation against the Mets on Saturday, Kimbrel had another shaky outing. Gattis contributed to the troubles — called for catcher interference when a swing ticked his glove — before Dietrich lined one off the wall in left-center. But, with runners at second and third and no outs, Kimbrel struck out the side to keep the game 2-2.
Miami squandered a chance in the eighth after Uggla botched a potential inning-ending double at second base. Umpire Marvin Hudson initially called the runner out, ruling that Uggla caught the ball but dropped it attempting to make the relay throw to first.
Marlins manager Mike Redmond challenged. After a delay of nearly 5 minutes, the call finally came down from the replay center: all runners safe. The video showed Uggla making the catch, but losing control as he grabbed the ball with his right hand — before he actually went into his throwing motion.
Instead of having runners at first and third with two outs, the Marlins were left with the bases loaded and one out. But Walden fanned Casey McGehee on a called third strike and got Jones on a grounder to Uggla, who stumbled a bit just beyond the infield dirt but made the inning-ending play.
With the game tied at 1, Heyward came through with an unlikely hit off Dunn, who made the left-handed hitter look feeble with two straight breaking pitches, then came in with a fastball on a 0-2 pitch. Heyward lined it for a run-scoring single, just his second hit in 19 at-bats this season off left-handed pitching.
NOTES: Braves LHP Mike Minor is getting close to rejoining the rotation. After going six innings for Triple-A Gwinnett over the weekend, he’ll throw a side session before tonight’s game against the Marlins. If all goes well, Minor would likely make his first major league start Saturday against Cincinnati. Minor, who went on the DL after experiencing shoulder soreness in spring training, noted how successful the Braves’ rotation had been in his absence. “I don’t want to mess things up,” he said with a smile. ... Florida C Jarrod Saltalamacchia was back at Turner Field for the first time since he was traded by the Braves in 2007 in a much-debated deal that brought Mark Teixeira to Atlanta. Saltalamacchia expected to be a little emotional when he stepped on the field. “This is where it started with me,” he said. ... The attendance was 16,055, the smallest crowd in seven games this season at Turner Field.