ATLANTA - The Mets' road woes continued Friday night, when a defensive meltdown in the eighth inning allowed the Braves to rally for a 2-1 victory.

Jacob deGrom tossed a gem on his 27th birthday, but an anemic offense and a shaky defense gifted him with an undeserved loss.

To make matters worse, the Mets likely will be without Jeurys Familia for the rest of the series. The closer experienced tightness in his left groin while bailing the Mets out of the eighth.

Manager Terry Collins initially said Familia was just battling cramps, but the pitcher said he wouldn't have been able to press on had the game gone to the ninth.

"I'll be OK soon," said Familia, whose emergence has held together an otherwise banged-up bullpen.

The loss of Familia only added to the bitter taste of the Mets' 14th loss in their last 17 games away from Citi Field. They have scored two runs in their last three games, all defeats.

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The Mets (36-33) own a half-game lead over the Nationals in the NL East, but that could change quickly without a turnaround from a sputtering offense that scratched out one run against Matt Wisler in his big-league debut.

The Mets brought a 1-0 lead into the eighth behind deGrom, who extended his recent stretch of dominance. But shortstop Wilmer Flores hesitated on a throw, centerfielder Juan Lagares appeared to misread a liner, and Collins pulled deGrom and watched the move backfire.

Jace Peterson won it with a two-run double off reliever Sean Gilmartin. Both runs were charged to deGrom, who was otherwise outstanding in 71/3 innings.

"My mechanics are sound right now," said deGrom, who has a 1.25 ERA in his last six starts.

Andrelton Simmons led off the eighth with a double off deGrom and advanced to third on a sacrifice bunt by Eury Perez.

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Charging hard off the mound, deGrom fielded the ball and had a chance to retire Simmons at third. But third baseman Ruben Tejada also charged at the bunt, leaving the base uncovered, and deGrom had to take the out at first.

Said Collins: "We made the right play."

But there was no debating the critical mistake by Flores, who helped the Braves extend their game-winning rally. "That's the second out of the inning,'' Collins said, "and it kind of takes the starch out of things."

Pinch hitter Pedro Ciriaco hit a grounder at Flores, who took so long freezing Simmons at third base that Ciriaco legged out a hit.

"That's my mistake not knowing the speed of the runner," Flores said. "I just took too long."

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Though deGrom looked sharp and had thrown only 97 pitches, Collins emerged from the dugout with his decision made. He didn't like the idea of deGrom pressing through the heat on a muggy night.

"I just thought it was time," Collins said.

So he opted for a lefty-lefty matchup, summoning Gilmartin to face Peterson, who lined a drive to center. Lagares appeared to come in on it, only to quickly retreat. By then it was too late, and the ball sailed over his glove. "I had no chance at that ball," Lagares said. "He crushed that ball."

Whatever the reason, it was yet another play the Mets needed to make, on yet another night in which they gave themselves no margin for their errors.

"In games like this," Flores said after his gaffe, "every mistake will cost you."