Power lunch.

Then a wild, winning dessert.

Gary Sanchez’s second season has been a challenge in many ways, but the Yankees catcher is working on the field and quietly behind the scenes to improve.

Sanchez arrived at Yankee Stadium early Friday afternoon to participate in extra hitting four hours before the Yankees’ magical 5-4 win over the Red Sox to move them 3 ¹/₂ games behind first-place Boston.

Sanchez had just come from lunch, and not just any lunch.

Sanchez spent quality time with Alex Rodriguez — in his new role as special adviser to Hal Steinbrenner — at Casa Lever restaurant in Midtown.

Asked the best advice A-Rod offered in regards to improving his game, Sanchez smiled and told The Post through an interpreter: “Alex, as you know, is a player with many, many years of experience and I would say anything in general coming from him would do me good. Everything is good.

“It was good to spend time with him.”

There was another special guest at the lunch, A-Rod’s girlfriend, Jennifer Lopez.

“Yes, she was there for a little bit,’’ Sanchez said with a big smile. “I’ve met her before.’’

A-Rod and J.Lo have been dating for three months. Rodriguez has jumped into his new life now that he is no longer a player. He is a broadcaster, a businessman and stays close to the game he loves.

Sanchez singled and scored the tying run in the Yankees’ stunning five-run eighth inning, highlighted by Aaron Hicks’ two-run home run, that erased Boston’s 3-0 lead. Sanchez also walked.

It was a good lunch and a good night. Watching it all from Hal Steinbrenner’s box was Rodriguez.

For the season Sanchez owns a .266/.346/.490 slash line. Last season when he took the AL by storm Sanchez managed a .299/.376/.657 slash line.

Sanchez, 24, also is having his troubles behind the plate. He is first in the AL in catcher’s errors (11) and passed balls (12).

Manager Joe Girardi elected Friday to have Austin Romine catch lefty Jaime Garcia.

“My plan is to catch Sanchee [Saturday],’’ said Girardi, who will send Luis Severino to the mound. “I felt that trying to run him out there five days in a row, and getting in late [after Thursday’s 4-0 loss to the Blue Jays in Toronto] would be somewhat difficult. So it just seemed like kind of a natural break. My thought is if he were to catch Jaime he would be much more familiar with him. It just felt like the natural thing to do, the natural break.’’

Getting away and talking to Rodriguez also was a “natural’’ break, getting advice from a peer instead of a coach or manager.

And it already has paid dividends.

So on the same day Rodriguez’s old Yankees teammate Derek Jeter was becoming head of the Marlins’ baseball and business operations as part-owner of the team in A-Rod’s hometown, he was trying to quietly help another former teammate.

A-Rod and his spokesperson were not available for comment.

Sanchez moved from designated hitter to catcher in the crazy ninth when Hicks saved the day by catching Andrew Benintendi’s sac fly at the left field wall and throwing out Eduardo Nunez at third base.

CC Sabathia has worked closely with Sanchez and offered this perspective on the young All-Star and the difficulties of the catching position.

“I think everybody gets on Gary for all the times he goes out to the mound, but he wants to get it right,’’ Sabathia said. “I just see that he wants to grow and get better. He takes it personally, which is something you need to do.’’

As for A-Rod counseling young players, Sabathia said: “A-Rod would be great for him, that’s who Sanchee has looked to.

That’s forever. Alex has been through every scenario.’’

Sanchez has 41 RBIs and 14 home runs over his past 55 games and his 18 home runs this season are the third-most by a major league catcher behind Salvador Perez and Willson Contreras (21 each).

On this day, the power lunch got Sanchez moving back in the right direction, as he got on base twice and contributed a key hit in a monster win.