NEW YORK – Luis Gil stood atop the Yankee Stadium mound in the fifth inning on Tuesday, feet spread wide across the rubber, the bases full of Mets. The young right-hander refused to wilt, exuding confidence that he could escape. He had a new and trustworthy weapon on his side.

After Gil was touched up by the Mets on June 26 at Citi Field, he sought out a former teammate, leaning upon Luis Severino for advice on how to better grip his slider. Severino delivered the goods in a series of video messages, helping Gil to harness a pitch that he leaned upon heavily in the Yankees’ 3-2 Subway Series loss to the Mets.

“The last start against us, the breaking pitches were not that good,” Severino said on Tuesday. “I just gave him some tips. The one that I’m throwing now has been really good. He went to the bullpen, he tried, and he told me after that it’s been unbelievable. So I’m really happy for him.”

Gil limited the Mets to one run across five innings, striking out six, before Jeff McNeil hit a two-run homer off Michael Tonkin in the sixth inning that held up as the deciding run. The Yankees have lost all three meetings with the Mets this season, with the clubs set to play one more game on Wednesday in the Bronx.

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With his pal Severino watching from the opposing dugout, Gil used Tuesday’s start to showcase his improvements.

“Severino is someone that I’ve always looked up to, ever since he was here, came up through this organization,” Gil said through interpreter Marlon Abreu. “He’s a pitcher with more experience than me. He has some knowledge to offer, and I took it into consideration and put it in practice here with our pitching coach [Matt Blake]. I’m getting really good results with that pitch.”

For a second consecutive start, Gil threw more sliders (40) than fastballs (31), also mixing in 20 changeups. He generated five swings-and-misses and eight called strikes with the slider, including using it as a finishing pitch for four strikeouts.

“I showed him how to manipulate it, and after that, it seems like he’s been really nasty,” Severino said. “I don’t know how he didn’t make the All-Star Game. He’s having a great season. Hopefully he can continue to do that.”

The 26-year-old Gil was dominant through his first 14 starts, going 9-1 with a 2.03 ERA through June 14, but he ran aground with a trio of bumpy starts against the Orioles, Mets and Reds, in which he allowed 16 runs across 9 2/3 innings.

With the assistance of Severino’s grip, Gil regained momentum with nine strikeouts against the Red Sox on July 7, then another seven facing the Orioles on July 13 in Baltimore.

“[The slider] has definitely gotten bigger while keeping the velo,’’ catcher Austin Wells raved after the Baltimore start. “He just added a third plus-pitch to his arsenal, and it’s only going to make him better.’’

Gil said that, though he now feels comfortable throwing the slider as a putaway pitch, he feels ready to execute all of his pitches at any point in the game.

“Nothing changes mentally,” Gil said. “You’re trying to attack guys; you’re trying to get ahead quick and get them to two strikes. You want to put yourself in the best position possible to get those guys out.”