When Jean Segura stroked a bases-clearing, three-run double in the first inning Monday, he couldn’t possibly have known that it would be only his second-biggest hit of the game.

Well, actually ...

Segura got to the ballpark earlier than usual for a Labor Day matinee in New York and was in full uniform 90 minutes before the game when Phillies teammate Rhys Hoskins came over and asked, “Whoa, why are you dressed so early? How many hits are you going to get today?”

“I said, ‘Well, I need five,’” Segura recalled, chuckling. “During the game, I told Rhys, ‘I’m going to get five hits! I’m going to get five hits!’ I was close. I only got four.”

But the Phillies needed each and every one of them, especially the last, a two-run home run in the 10th inning to defeat the Mets, 9-8, and salvage a four-game split at Citi Field, after they blew a six-run lead.

Wins rarely come easy for these Phillies, so why would this one be any different? But after dropping back-to-back games to the Mets over the weekend, including a 14-1 drubbing with Aaron Nola on the mound on Sunday — and with the first of five doubleheaders in 15 days on tap Tuesday at Citizens Bank Park — it also felt like a victory that they needed to have.

“Basically this season, every game’s a big game, especially right now,” said starter Zack Wheeler, who cruised through four innings, ran into trouble, and was lifted after the sixth despite throwing only 83 pitches. “We’re in the last little stretch, and we need to win ballgames. I think everybody in here knows that. That’s why we kept our head down today and grinded that one out.”

Staked to a six-run lead, Wheeler gave up four doubles in the fifth inning, including three in a row to Michael Conforto, J.D. Davis, and Dominic Smith, as the Mets halved the margin to 6-3. When that part of the order came around in the seventh inning, manager Joe Girardi turned to the bullpen, a move that only two weeks ago would’ve been unthinkable at best, self-destructive at worst.

“I’ll be honest with you, I was a little surprised,” Wheeler said of not going out for the seventh inning. “But obviously it’s [Girardi’s] call, so you’ve got to respect it.”

Wheeler “wanted to stay in. It was a decision that we made,” Girardi said. “I always like Wheels. Always. But I just felt that he just wasn’t quite the same, and we made a change, and you saw what happened.”

Girardi put his trust in lefty JoJo Romero, who was appearing in only his fifth career major-league game but didn’t give up a run in his first four. Romero gave up two hits and a run with assistance from shortstop Didi Gregorius’ throwing error. In came newly acquired reliever David Phelps, who walked dangerous Pete Alonso before Jeff McNeil’s three-run homer gave the Mets a 7-6 lead.

It took a two-out single by unflappable rookie Alec Bohm to tie the game in the eighth inning. And it took Segura’s line-drive off the wall behind the left-center-field fence on a 97-mph sinker from Mets reliever Miguel Castro to restore the lead, which Hector Neris held despite giving one run back in the bottom of the 10th.

Segura isn’t the first name that comes to mind when you think about the Phillies’ high-scoring offense. Entering play Monday, he was batting .237 with a .708 OPS, numbers that would continue a four-year decline in his offense.

But Girardi has lauded his willingness to begin the season at third base, a position that he hadn’t played, only to shift over to second base after Bohm was called up last month.

Oh, and good luck finding a bigger hit for the Phillies this season than Segura’s shot against Castro.

“I think he has probably been overlooked a little bit, but not by us,” Girardi said. “What Jean has done has been really important, because he has given us so much flexibility. And I give him a lot of credit, because it’s not easy changing where you play defense on a regular basis, but he’s done that. And he’s come up with some big hits. Today, he had two big hits.”

Indeed, it marked Segura’s first four-hit game since June 24, 2019, also against the Mets. He drove in five runs, a career high. And as he rounded the bases, Hoskins raised both hands in recognition of their pregame conversation.

“I usually get dressed like 45 minutes, 30 minutes before the game starts,” Segura said. “So, my teammates were freaking out like, ‘What’s he doing? Is he okay?’ I don’t know. Maybe I’ll start doing it earlier now.”