CINCINNATI — Laynce Nix had never made such a joyous, impromptu trip around the bases.

His pinch-hit homer in the bottom of the 11th inning powered the Cincinnati Reds to a 3-2 victory over the New York Mets on Monday night and provided a first-ever home-plate pummeling for Nix, who had never homered to end a game.

“That’s the best!” Nix said after getting engulfed in a joyous scrum at home plate.

That’s how the Reds have done it all season.

Nix’s one-out homer on a hanging curve from Manny Acosta (1-1) left the Reds 3-0 in extra innings. Eight of their 11 wins have come in their final at-bat.

This one surprised even Nix, whose drive barely cleared the wall in right-center field.

“I didn’t think it was going out,” said Nix, who watched it the whole way. “I thought it was too high, but it carried far enough.”

Nick Masset (3-1) pitched the last two innings, giving up two singles in the 11th before pitching out of another Mets threat. Then, he watched Nix end it with a drive that barely made it.

“I knew it was out,” Masset said. “If you get it up in the air here, it can go out.”

New York stranded runners in scoring position in the sixth, seventh and 11th innings, forcing the Mets to settle for two runs in one of the majors’ most hitter-friendly ballparks.

“We at some point have got to push a run across late in this ballpark,” Mets manager Jerry Manuel said.

Drew Stubbs also homered for the Reds, leading off the first inning with the first one allowed by Oliver Perez this season. Joey Votto also had an RBI single off the left-hander, who lasted six innings and remained winless in six starts since Aug. 18.

Both teams have taken similar bottom-to-top paths in the last two weeks.

The Mets won eight in a row, going from last to first in the NL East. Two losses at Philadelphia over the weekend dropped them a half-game behind the Phillies heading into the Cincinnati series. The Reds won five straight, climbing to second place in the NL Central, before dropping their last two at first-place St. Louis.

Which one would keep falling?

The Mets were playing on little rest. They lost in Philadelphia 11-5 on Sunday night, and didn’t get to their hotel in Cincinnati until nearly 4 a.m.

The offense looked a little sleepy, but that wasn’t new. Four of the Mets’ eight starting position players were batting .257 or less heading into the game.

“We’ve just got to find a way to get runners on,” said Jeff Francoeur, who singled home the first run. “And not just get runners on, but get them on to start an inning. We’ve got to get so many two-out hits.”

The Reds gave them a little help to get going.

Stubbs initially broke the wrong way on Ike Davis’ liner to center with two outs in the second inning. Stubbs never fully recovered, the ball deflecting off his glove for a two-base error. Francoeur singled off Mike Leake to tie it 1-1, only his fourth hit in his last 18 at-bats.

Jose Reyes doubled home another run in the sixth, tying it at 2. But the Mets’ offense stopped there.

Leake, who made the jump from Arizona State directly to the majors, had another solid showing. The unbeaten right-hander gave up four hits and two runs — one earned — in six innings, lowering his ERA to 2.94.

NOTES: Mets RH Mike Pelfrey had a precautionary MRI on his right shoulder, which felt a little stiff during his start on Saturday. He’s expected to make his next start. … RHP Kelvim Escobar will have surgery on his right shoulder Wednesday and miss the rest of the season. Escobar came to the Mets’ camp on a minor league contract but developed shoulder problems in March. … 3B David Wright made the best play of the game, catching Stubbs’ grounder down the line and making a throw from foul territory while his momentum carried him away from first. Got him by a step. … New York’s Jason Bay saw his hitting streak end at nine games. … Reds OF Chris Dickerson had surgery on his right hand and wrist. He’s expected to be sidelined for at least a month. … RF Chris Heisey made his major league debut, going 0 for 5. He was the Reds’ minor league player of the year last season.