ATLANTA — Mickey Callaway is a jinxed man.

Every bullpen decision the Mets manager makes these days seems to detonate in his face, the latest coming Monday when Seth Lugo was left in the game to pitch a second inning of relief — leaving Jeurys Familia in the bullpen — and surrendered a walk-off two-run homer to Charlie Culberson in the ninth in a 4-3 loss to the Braves in the first game of a scheduled doubleheader at SunTrust Park.

“Things just aren’t going our way,” Callaway said after the Mets (25-25) lost their fourth straight and fell to .500 for the first time this season. “I think they will snap out of it eventually. It’s tough right now, I am sure they are feeling a lot of pressure that they’ve got to get the job done, and they will.”

After a franchise-best 11-1 start to the season, the Mets have cratered in recent weeks, with Callaway’s bullpen management coming into question on a consistent basis. But the Mets are also struggling to score runs, with Yoenis Cespedes and Todd Frazier on the disabled list — they were joined by Wilmer Flores on Monday.

“Right now, the way things have been going, I feel OK that we’re 25-25, to tell you the truth,” Callaway said. “That is how bad it’s been going.”

Lugo had pitched a career-high 17 straight scoreless innings before allowing a run in the eighth that tied it 2-2 and ensured a no-decision for Jacob deGrom after another superb performance. The right-hander had bulldogged through the seventh and gotten three straight outs with runners on base after allowing a leadoff homer to Tyler Flowers.

Overall, the Mets ace allowed one earned run on five hits with eight strikeouts and three walks, departing after 115 pitches. It was the second straight start in which deGrom pitched brilliantly, but the Mets lost after squandering a late-inning lead. The other came Wednesday against the Marlins, when Familia allowed two runs in the ninth.

“It’s frustrating,” Lugo said. “[DeGrom] is doing what he always does and we have to be better than that, those are the games we have to win.”

On Sunday, the Mets lost to the Brewers after Callaway inserted struggling lefty Jerry Blevins in the seventh inning instead of sticking with dependable Robert Gsellman. And on Friday, the manager picked erratic AJ Ramos to pitch in the 10th inning over Familia and watched the right-hander walk in the winning run.

Callaway said the plan Monday was to use Lugo for a two-inning save if deGrom got through seven. If deGrom went shorter, Callaway’s plan was to cobble together outs, use Familia to close and then let Lugo start the nightcap of the doubleheader, for two innings.

“We had one of our best relievers in the game and we just lost it,” Callaway said.

After Lugo allowed two hits in the eighth and saw the Braves tie it 2-2 on Nick Markakis’ sacrifice fly, Devin Mesoraco led off the ninth with his fifth homer in 15 games with the Mets.

Lugo was in immediate trouble in the bottom of the inning, walking Johan Camargo leading off. With one out, Culberson crushed a 1-2 slider into the seats in left-center to end it.

“I was trying to throw it out of the zone,” Lugo said. “It went into the zone, it was a bad pitch and good swing.”

Luis Guillorme’s RBI double in the fourth gave the Mets a 2-0 lead against lefty Max Fried. Mesoraco singled and scored on Guillorme’s line drive to left field, on which Preston Tucker started in before retreating too late.

The Mets got a run in the first inning without a hit, when Mesoraco drew a two-out walk with the bases loaded. But the Mets also left the bases loaded in the inning.