MIAMI  -- If it's not time for the Braves to panic, it's at least time to be seriously concerned.

Omar Infante hit a two-run homer off Atlanta closer Craig Kimbrel with two out in the ninth inning on Monday night to give the Marlins a stunning 6-5 win over the Braves, whose wild-card lead is down to 2-1/2 games over surging St. Louis.

It was the second homer in as many days off Kimbrel, who had previously allowed only one homer all season.

Infante, the former Braves infielder, homered following a two-out single by Emilio Bonifacio that originally was ruled an error on Braves third baseman Chipper Jones. Jones lost the chopped grounder in the lights, and the official scorer changed the ruling to a hit.

"When you play baseball in a football stadium that can happen from time to time," said Jones, who'd had it happen to him before at Miami and at San Diego, when the Padres played in a multi-purpose stadium used for  football. "But it's extremely bad timing. Pretty helpless feeling when the game should be over. I had no clue where the ball was until it bounced....

"It’s a funny game. Just when you think you’ve got it figured out, it’ll kick you in the gut.”

Kimbrel (4-3) retired the first two batters in the inning and would have had his majors-leading 45th save if Jones hadn't  lost Bonifacio's ball in the lights. The rookie closer didn't see it that  way, however.

“I don’t even think about that [play]," he said. "I just needed to put it behind me and get the next guy out. I was behind in the count [1-0 to Infante], trying to get ahead. He did what he did with it."

Infante's first-ever walkoff homer was a potentially devastating blow to his former team.

The Braves drew three walks during a two-out rally in a four-run seventh inning, and it looked as if they’d win a game much the same way they had lost a day earlier against the  New York Mets.

Instead they lost for the 12th time in 18 games, and their magic number to clinch the National League wild card remained stuck on seven with eight games left. Any combination of six Braves wins and Cardinals losses would clinch a postseason spot for the Braves, but lately there have been mostly Atlanta losses and Cardinals wins.

"We've just got to win ballgames and close them out," Braves manager Fredi Gonzalez said. "But today was just one of those things. You can’t sit here and explain it. You can't defend that, a chopper in the lights. I've seen it happen here before."

It was the Braves’ first loss in seven games this season at Sun Life Stadium, where Gonzalez managed the Marlins for 3-1/2 seasons through June 2010.

The Braves can now feel the Cardinals breathing down their  necks. St. Louis, which was 10-1/2 games behind Atlanta, Aug. 25, has won 15 of 20 games including three in the past four days at Philadelphia.

"We’ve got to win, there’s no sense in scoreboard-watching," Gonzalez said. "We’ve got to win our games and our series, and keep going forward.”

The Braves quickly went from a potentially uplifting win to another deflating loss.

"We fell behind, then we fought to get back and took advantage of some of their mistakes," Jones said. "You felt like tonight was going to be our night to win one maybe we should have lost. One strike away and you lose a ground ball in the lights. That makes you think that the baseball gods have been on our side for 154 games, and now they’re turning their back on us.”

"You’ve still got the 3-1/2-game lead -- and then all of a sudden it’s gone."

Marlins slugger Mike Stanton hit tape-measure solo home runs off Braves rookie Mike Minor in the first and third innings for a 2-0 lead. His first inning homer sailed into the upper deck in left field, the first upper-deck homer at the stadium this season.

"It contributed to finally getting these guys in the late inning," Stanton said of his fourth career multi-homer game. "It seems like déjà  sometimes. We'll get up and they'll creep back and in the 7th 8th or 9th they'll come back on us.

"This was good to get that turned around and at least be the spoilers. We’re obviously out, so maybe do something to impact the playoffs a little bit.

Still, it was an 0-2 fastball to Logan Morrison in the sixth that was Minor’s costliest mistake.

Jason Heyward’s homer off Florida starter Ricky Nolasco in the top of the sixth had trimmed the lead to a run, but Morrison belted Minor’s fat fastball for a two-run homer and a 4-1 Marlins lead.

The Braves weren’t done. Dan Uggla led off the seventh with a homer, his fifth in 16 games this season against his former team. Uggla has a career-high 35 homers in his first season with the Braves, after being traded from Florida in November.

A pair of groundouts later, the Braves began a two-out rally with a single by Alex Gonzalez, another former Marlins infielder. Heyward and pinch-hitter Brooks Conrad followed Gonzalez with walks to load the bases against Nolasco, and the Marlins made a pitching change.

They brought in Michael Dunn, the lefty who was traded to Florida along with Infante in the deal for Uggla. Michael Bourn, the only batter Dunn faced, hit a broken-bat infield single to drive in a run and bring the Braves within 4-3.

Right-hander Ryan Webb replaced Dunn and walked Martin Prado with the bases loaded to tie the score. Jones grounded to second baseman Infante, who booted the ball, allowing the go-ahead run to score. The Braves had a four-run inning and a 5-4 lead.

On Sunday against the New York Mets, the Braves blew a 5-4 lead in the eighth inning, when Jonny Venters allowed two runs and three walks, including a bases-loaded walk. Kimbrel also gave up a homer in the ninth inning of Sunday’s 7-5 loss.

Venters bounced back with a perfect eighth inning against the Marlins, but Kimbrel suffered his seventh blown save.

Minor was charged with four runs, six hits and two walks in 5-2/3 innings. He got no decision and the Braves fell to 9-2 in his past 11 starts (he’s 5-0 in that stretch).

Heyward’s homer was his 14th and first since Aug. 23 at Chicago’s Wrigley Field. He had gone 55 at-bats without a homer before Monday, and had hit just two in 127 at-bats since homering in consecutive games July 21-22.

While he  hasn’t been hitting for power, Heyward has been getting on base a lot lately. He was 1-for-3 with a walk Monday, and is 10-for-35 with 12 walks and an OBP in the mid-.400s during his past 13 games.