NEW YORK -- Pete Alonso's upper body was bare, save for a compression sleeve wrapping his left elbow and a batting glove on each hand. Amidst the chaos of the Mets’ 5-4, walk-off win over the Phillies at Citi Field, Alonso had little idea which of his teammates had actually

NEW YORK -- Pete Alonso 's upper body was bare, save for a compression sleeve wrapping his left elbow and a batting glove on each hand. Amidst the chaos of the Mets’ 5-4, walk-off win over the Phillies at Citi Field, Alonso had little idea which of his teammates had actually ripped the jersey off his back. He knew only that at some point as he stood and celebrated, ringed by teammates, he had become bare-chested on the field.

He embraced it. When Noah Syndergaard ran over and dumped a jug of water on him, Alonso grinned and raised both hands into the air.

• Box score

“It’s a fun thing,” Alonso said. “Hopefully I can rip some more shirts off and they can rip some shirts off me by the end of this thing.”

Ever since Alonso disrobed Michael Conforto following a walk-off single last month, the rookie’s teammates “forewarned” him that, should roles one day reverse, he and his clothing would surely also part ways. So it was on Friday night, when Alonso drew a walk-off walk in the ninth inning and thus started another manic celebration on the field. The victory, combined with a Cubs’ loss, moved the Mets within four games of a Wild Card berth with 22 to play.

“You just kind of figured that he was going to do that,” manager Mickey Callaway said.

That Alonso was even in position to do so was the product of a game that saw the Mets take an early two-run lead, give it back, then retake it on RBI hits from Alonso and Wilson Ramos in the eighth. The Mets watched Edwin Díaz blow his second consecutive save opportunity by giving up a two-run J.T. Realmuto homer.

But with extra innings looming, the Mets received a spark as Juan Lagares and J.D. Davis hit consecutive two-out singles in the ninth, and Nick Vincent hit Jeff McNeil with a pitch to bring Alonso to the plate.

Alonso -- he of 45 home runs and now 107 RBIs, a favorite to win the National League Rookie of the Year Award and a candidate to receive some down-ballot MVP votes.

“I’m sure the pitcher’s like, ‘Oh no, it’s Pete Alonso coming up,’” Callaway said.

Neither of Vincent’s first two pitches tempted Alonso, who took them for balls as the crowd stirred. The next pitch was an 89 mph fastball, middle-in, which Alonso offered at and missed. In retrospect, it was the best pitch he’d see. Alonso spoiled an outside fastball, then took another well below the zone.

“I was like, ‘All right, he’s got nowhere to put me,’” Alonso said. “He’s either got to lay one in there, or if it’s not right there, then I’m going to take it.”

Vincent chose the latter option, delivering a shoulder-high fastball that Alonso took for ball four. As the Mets poured out of their dugout, Tomas Nido and Luis Guillorme grabbed for his jersey and ripped it from both ends. Alonso conducted multiple on-field interviews in that state, remarking that he didn’t feel cold on the rainy, damp night because, “I’m a polar bear.”

That polar bear is also perhaps the most significant reason why the Mets, at 72-68, still have a chance in the NL Wild Card race. Given that they don’t play the Wild Card-leading Nationals and Cubs again this season, the Mets know they will need help from other teams to make it to October. Third baseman Todd Frazier , who admitted to scoreboard watching, said that the Mets “have to think sweep, and we’ve got to think sweep a lot” if they are to make the postseason tournament.

To accomplish that sort of thing, they will also need Alonso to continue contributing -- whether via homers, walks or any other means.

“The sky’s the limit for him, man,” Frazier said. “He’s going to be a really good hitter. He already is.”