Edwin Diaz and Tomas Nido of the Mets celebrate after defeating...

Edwin Diaz and Tomas Nido of the Mets celebrate after defeating the Yankees at Citi Field on Tuesday. Credit: Jim McIsaac

The moment unspooled in slow motion, like a car crash, as Edwin Diaz spun around toward second base to start a potential game-ending double play Tuesday night.

But as the Mets closer hurriedly changed his grip, from full palm to two fingers —  for accuracy —  the baseball flipped backward out of his hand, in slapstick fashion. As a result, the Yankees would get the tying run to the plate in the ninth inning. Twice.

Everyone’s initial reaction? This was about to be another Luis Castillo moment for the Mets, the Diaz gaffe triggering flashbacks to the 2009 dropped pop-up that allowed the Yankees to circle the bases for an impossible Subway Series victory in the Bronx.

And Diaz?

“I started laughing,” he said.

That’s right. No flinching with this matured Diaz, and no panic among these Mets, who rose to the occasion Tuesday night, on the Subway Series stage, as the Yankees shriveled under the spotlight at Citi Field. Any history between these two teams, any past failures, remained just that. This is a different season for the Mets, who shook off a pair of back-to-back, first-inning homers by Aaron Judge and Anthony Rizzo to score four runs in the bottom half and never looked back in the 6-3 victory.

Of course, Diaz sealed it, for his 22nd save, striking out both Rizzo and Gleyber Torres. How did he recover so quickly from fumbling a ball in front of 42,364 stunned onlookers?

“Just forget about that,” Diaz said. “Make pitches and win the game.”

That mantra has served Diaz so far, and the Mets were just as unfazed by the Yankees’ opening punches. Starling Marte and Eduardo Escobar responded by crushing homers in that first inning, and the Mets scored another run in the third inning when a Josh Donaldson throw on a routine grounder caromed off the side of Francisco Lindor’s helmet. Jeff McNeil added some insurance with his two-out RBI single in the eighth, the inning after he made a dazzling barehanded scoop and flying cross-body throw.

“That should be a SportsCenter Top 10 play,” Pete Alonso said afterward.

This was not just another win for the Mets. As badly as they needed it to keep Atlanta at bay for another night —  the division lead remains at two games —  the spiritual boost was evident in the postgame clubhouse. But in a low-key way, the kind of calm confidence born of doing a big job you knew you were capable of. The music was off. This wasn’t a dance party. It was a step on the way to greater goals.

“These games are a real good test for us,” said Alonso, who went 3-for-3 with an RBI double, a walk and a run scored. “If we can beat a team like that, we can get where we want to be.”

The Yankees still have baseball’s best record, but the Mets outclassed them Tuesday night in every category. Taijuan Walker went six innings for the ninth consecutive start while Jordan Montgomery only got seven outs before he was gone. The Yankees went 0-for-8 with runners in scoring position, and in the game’s pivotal managing decision, Aaron Boone chose to send up Joey Gallo to pinch hit for Isiah Kiner-Falefa with one on and two outs in the eighth, prompting Buck Showalter to bring in Diaz.

Advantage, Showalter.

In one of the most predictable matchups you’ll ever witness this season, Diaz whiffed Gallo on five pitches, the last on a wicked 93-mph slider. Just unfair, right from that first 100-mph fastball.

Showalter doesn’t like to push Diaz for more than one inning, but felt he was rested enough to play that card Tuesday night. The stage no doubt was a factor, too. Showalter doesn’t like to feed the media hyperbole surrounding events like the Subway Series, but he had to admit the long-term benefit of knocking around the Yankees, even if this was just one game in late July.

“We’ll see,” Showalter said. “Pressure is what you make of it —  it’s a privilege. Like I told the players in the advance meeting, it’s a privilege to play in this environment. Have fun, draw something from it and be able to reach back for it as we go forward. Hopefully, we’ll be able to use it if we get an opportunity to do what we’re trying to do.”

Watching the Mets do what they did Tuesday night, in the Subway Series opener, makes that seem more possible. And Citi Field did a spot-on October impression. Escobar said his first-inning blast felt like a “World Series home run.” Even Alonso, who didn’t quite know quite what to compare the energy to, only knew he wanted more of it.

“I’ve never played in a major-league playoff game before, but if I had to guess, this was similar,” Alonso said. “I’m looking to change that this year.”

And it’s a little easier for the Mets to imagine after Tuesday night.

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