Mets’ Starling Marte, Pete Alonso and Mark Vientos celebrate their...

Mets’ Starling Marte, Pete Alonso and Mark Vientos celebrate their 2-1 win against the Philadelphia Phillies on an MLB baseball game at Citi Field on Sunday, Sept. 22, 2024. Credit: Kathleen Malone-Van Dyke

Why not the Mets? Why can’t Carlos Mendoza & Co. make good on their pledge to play again this year at Citi Field?

Circle Oct. 8. Game 3 of a Division Series. That’s probably the earliest the Mets could get back to Flushing. Then again, after Sunday night’s thrilling 2-1 victory over the Phillies in their regular-season swan song in Flushing — which prevented a division clinch and sent the visitors back down the Jersey Turnpike with their cases of champagne still sealed — we’re not ruling out catching the Padres to host the wild-card round in Flushing.

Anything feels possible now after Edwin Diaz blowtorched his way through the top of the Phillies’ lineup en route to a six-out save, only the second of his career — 24 hours after getting four outs to seal Saturday’s win.

The Mets are in uncharted territory, but after beating Zack Wheeler to take the weekend series and post an MLB-best 15-5 record in September, they sure look comfortable at the wheel.

The destination? Returning to Citi Field in 2024, with Sunday’s October atmosphere actually taking place in October.

“That’s the goal, right?” said Brandon Nimmo, whose sixth-inning home run — his third in five games — turned out to be the game-winner. “There’s a lot of hoops to get through in order to do that, but there is no doubt that is our goal.

“We have to take care of business and be present in the situation. Otherwise, it will not happen. But that is the goal, to bring October baseball, playoff baseball, back to New York.”

Citi Field sounded ready for it Sunday night, with a second straight sellout crowd (43,139) welcoming Pete Alonso to the plate with a standing ovation in the first inning, enough for him to step outside the box and wave his helmet. The fans chanted his name all night, and Alonso, who might have been playing his final game at Citi Field in a Mets uniform, appreciated the gesture, even if he didn’t give much back with three strikeouts.

“It’s right out of a storybook for me,” Alonso said. “It’s something you hear about or read about or see in movies.”

The Mets’ rotation also has taken on a mythical quality. Entering Sunday’s start by Tylor Megill, their starters had pitched better and longer than just about anyone else in the majors since Sept. 1, with a 2.28 ERA that was second only to the Padres (2.25), the lowest WHIP (0.90) and the most innings (118 1⁄3). Offensively, the Mets ranked third overall in homers (28) and runs scored (101), with the seventh-best OPS (.748) in September.

If this winds up being Alonso’s long goodbye, he wants to stretch it out as much as possible, and despite Francisco Lindor’s indefinite absence, the Mets are playing like a team that could stick around for a while. The only downer Sunday night was listening to Lindor after the game, as his return — if it ever happens — is likely to be in a limited capacity.

“If I play this year, I don’t think it’s going to be pain-free,” he said. “I’m OK with that. I just don’t want it to be a constant pain where I can’t bend over, and then I put my teammates in a position where I’m not helping them as much as I can. That’s not fair for anybody.”

Losing Lindor figured to be a death knell to the Mets’ wild-card hopes, but they’re 6-1 since their MVP was replaced in the starting lineup.

Sometimes, when teams get hot at this time of year, they’re able to fuel that fire deep into October, but this isn’t just a recent phenomenon. The Mets are 63-34 since June 2 and have the best winning percentage (.649) in the majors in that span, so this is more like a continuation of a series of successful trends at the pivotal stage of the season.

“I think everybody is doing their part to push us forward,” Luis Severino said. “Hopefully to get to the playoffs, move on and keep going.”

Does that mean returning to Citi Field in October? “Yes, of course, 100%,” Severino said. “We’re going to do everything in our power to bring at least one playoff game to New York.”

The confidence is there, as is the momentum. But the Mets still need to lock down a wild-card berth, and for all they’ve already accomplished — roaring back from a 24-35 record on June 2 — the road to the finish line is a bumpy one. A series win in Atlanta would secure a wild-card spot, but with anything short of that, it gets tricky.

Atlanta should have a much tougher draw for that final weekend, as it will host the Royals, who should still be jockeying with the Tigers and Twins for a wild-card berth, or playoff position at the very least. With the Brewers a virtual lock for the NL’s third seed, they could be more worried about October prep on that final weekend than knocking out the Mets, who are rolling right now.

“They’re resilient, they care, they have passion,” Mendoza said. “And when the moment seems to be really big, they continue to show and they continue to find a way. I’ve been really impressed and proud of them . . . But we still have work to do.”

A lot of it for the Mets to get back to Citi Field. But the task in June was monumental, too. And look where they are now.