NEW YORK -- Although Francisco Alvarez had to reach down to hit his seventh-inning double on Saturday, dipping below the strike zone to lift an Orion Kerkering sweeper to left-center field, he caught enough of the pitch to strike it with some authority. As the ball headed toward the gap, Alvarez kept thinking: “No way he’s going to catch it.”

That may not be the type of thought Alvarez would have had a month ago, when he was still deep in a slump that consumed much of his season. But these days, Alvarez has reason for optimism. His hot streak, which included a homer, a double and three RBIs in a 6-3 win over the Phillies, is one of the foremost reasons why the Mets are streaking toward a potential playoff berth.

“He’s almost foaming at the mouth to get up there,” teammate Brandon Nimmo said. “It’s unbelievable. He wants it.”

• The Dark Knight returns -- and plans to do so more often

The win allowed the Mets to maintain a two-game lead over the Braves for the final National League Wild Card spot with seven to play. That’s in large part thanks to Alvarez, who has five home runs in his past 11 games after hitting just six in his first 85 contests. He has raised his OPS 50 points in 10 days.

Saturday, Alvarez tied the game in the second inning with a 113.8 mph homer, the hardest of his career (surpassing the 111.7 mph home run he hit two days prior). But his more significant impact may have occurred in the seventh, when he came to the plate moments after Nimmo gave the Mets a late lead with a go-ahead RBI single.

With two men on base and two outs, Alvarez lifted his double into the gap to score two crucial insurance runs. Upon reaching second base, he raised both hands in the air and pointed to the dugout, where Francisco Lindor and others were screaming back at him.

“Unbelievable,” manager Carlos Mendoza said of the reaction from a sold-out crowd of 44,152, the fifth largest for a regular-season game in Citi Field history. “That’s what it should look, it should feel like -- especially when we’re playing meaningful games in September late in the season, fighting for a playoff spot. It’s what you signed up for. It’s what you dream, you prepare for.”

It wasn’t just Alvarez who elicited those cheers. Starting pitcher Sean Manaea earned his share with seven-plus effective innings, tipping his cap to the crowd as he departed in the eighth. Nimmo had his go-ahead hit, Luisangel Acuña homered for the third time in his first eight career games and Edwin Díaz was electric in nailing down a four-out save.

But it was Alvarez who changed the entire look of the thing.

When Lindor suffered his back injury last weekend, it generated two pressing questions. One was how long Lindor might be sidelined. The other was who might step up in his absence.

One candidate, J.D. Martinez, is slumping so badly that Mendoza has benched him twice in a week against left-handed starters -- something that would have been unthinkable at virtually any other point of Martinez’s career. Another, Pete Alonso, hasn’t always come through in the highest-leverage spots (despite reaching base in all five of his plate appearances Saturday). Nimmo has been inconsistent. Mark Vientos has cooled from a hot midsummer streak.

That has left Alvarez to take the mantle, which he has done with aplomb. Since the night Lindor injured his back, Alvarez has gone 7-for-24 with four home runs and 10 RBIs.

“Hard-working kid,” Mendoza said. “He’s been working really hard behind the scenes for a month. And finally, it’s paying off. … I don’t think this is an overnight thing. But it’s fun.”

Specifically, Alvarez has worked to improve both his plate discipline and his swing mechanics, trying to open his hips later so that he can “feel powerful” again. He certainly has both the track record and the reputation. After speaking about his own power stroke as a rookie, Acuña laughed when asked about Alvarez. “Now he’s got power,” the younger player replied with a laugh.

For the Mets, that muscle is showing up in games at the most opportune times. Nimmo described the way Alvarez stalks around the batter’s box as proof that he relishes the big moments, which are happening more and more for a Mets club that continues to look the part of a playoff team.

“I like it,” Alvarez said. “I like to play every day. I like those games. And I love the race, too.”