ATLANTA — Robert Gsellman’s rubber arm and baggy shirt were a perfect combination for the Mets in extra innings Friday night.

After pitching the 10th and 11th, the right-hander remained in the game to bat, leading off the 12th, and was told to expect another two or three innings of work if the game kept going.

In short succession, Gsellman got hit by a pitch, scored the go-ahead run and received the win in the Mets’ 5-3 victory over the Braves at SunTrust Park.

Yoenis Cespedes’ RBI single brought in Gsellman before Asdrubal Cabrera’s double gave the Mets a cushion.

“It’s fun to be out there on the bases and run and be part of the game,” Gsellman said, noting that he is among the Mets’ fastest pitchers.

Josh Ravin clipped Gsellman’s jersey with a fastball to put the go-ahead run at first before Amed Rosario’s sacrifice bunt moved up the runner.

“The athleticism, even to send [Gsellman] up to hit, makes a difference,” manager Mickey Callaway said.

Gsellman, who pitched two scoreless innings, became the first pitcher in two years to score the go-ahead run in a game and record the win. Matt Albers had last done it, for the White Sox against the Mets on June 1, 2016.

Cespedes, who entered 3-for-30 (.100) on the road this season, walked in his first plate appearance Friday and then struck out four times before delivering against Ravin in the 12th.

Tomas Nido became the first Mets catcher this season to throw out a base stealer when he nailed Ryan Flaherty attempting to swipe second in the seventh. Mets catchers were 0-for-21 to that point (but credited with two throw outs that were actually pickoffs). Nido repeated his magic in the eighth, throwing out Ozzie Albies attempting to steal second after Seth Lugo had walked the leadoff hitter for a second straight inning.

Noah Syndergaard lasted six innings and allowed three earned runs on seven hits with six strikeouts. The right-hander was removed after 103 pitches in a tie game. It marked the third time in five starts Syndergaard lasted six innings, but he is yet to pitch beyond that point this season.

“I am kind of disappointed and frustrated,” Syndergaard said, referring to his body of work this season. “I feel like I’ve had some dominating stuff, but I really haven’t dominated out there.”

Syndergaard unleashed a wild pitch in the sixth that helped the Braves tie it 3-3. Nick Markakis doubled leading off the inning and reached third with nobody out when Syndergaard planted a sinker in the dirt that Nido couldn’t handle. Kurt Suzuki’s sacrifice fly brought in the run.

Wilmer Flores was thrown out at the plate to end the sixth, negating a bloop double to left for Jay Bruce, who snapped an 0-for-19 drought. Flores, running from first base, was hit with as swipe tag by the catcher Suzuki as he slid headfirst into the plate.

Bruce’s defensive miscue in the fourth helped the Braves pull within 3-2. Flaherty hit a line drive to right on which Bruce started in and then froze as the ball sailed over his head for an RBI double. Dansby Swanson, who had delivered a two-out single, scored on the play.

Flores’ RBI single in the top of the inning gave the Mets a 3-1 lead. Todd Frazier walked and stole second to begin the rally before Flores singled and was thrown out trying to extend the hit into a double.

Rosario stroked an RBI double in the third that delivered the Mets’ first run. Michael Conforto’s sacrifice fly gave the Mets a 2-1 lead. Nido singled leading off the inning — a rare hit by a Mets catcher — to start the rally.

Albies homered on a 100-mph fastball from Syndergaard in the first inning to get the Braves their initial run.

Lugo and AJ Ramos combined for three innings of scoreless relief before Gsellman entered, and Jeurys Familia worked a perfect 12th for his eighth save.

“[Gsellman] could have gone another two or three innings and that is what we were counting on,” Callaway said. “We had to send him up there [to bat] and he did a good job of getting hit with the ball.”