Rafael Nadal will take out Italian upstart Matteo Berrettini in Friday’s semifinals, win the U.S. Open, equal the great Roger Federer next year in Grand Slam titles and pass the Swiss Maestro soon after.

That’s how much ESPN’s tennis voice, Patrick McEnroe, believes in the Spanish warrior, whom he picked to win the Open before the first ball was struck. To boot, McEnroe thinks Nadal will make quick work of the first Italian male semifinalist at the Open since 1977.

“Nadal’s playing as well as he’s played in a while here,’’ McEnroe told The Post. “I picked him to win before the start, and nothing I’ve seen changed my mind. I think Berrettini will be a solid player. It’s hard to see how he’ll break Nadal down the way he’s serving.”

Technically, McEnroe thinks the Nadal lefty factor will favor him and “expose Berrettini’s backhand. He’ll be able to get the ball to Berrrettini’s backhand a lot more than other players with his forehand topsin crosscourt,’’ McEnroe said. “I’d be surprised if [Berrrettini] won a set.’’

The 23-year-old from Rome has been a Flushing feel-good story as he makes his Grand Slam semifinals debut after surviving a five-setter with Gael Monfils.

“For him, it’s already a success,’’ McEnroe said. “For Nadal, the tournament is just starting.”

Indeed, the celebration by the locker room after Berrettini’s five-set win Wednesday was full of Italian tears. He gave half-minute bear hugs to his entourage that included his coach, Vincenzo Santopadre, and Carroado Barazzutti, the last Italian man to play an Open semifinal and who is now Davis Cup captain.

Also amid the frenzy was Giovanni Bartocci, who owns an Italian restaurant on the East Side that Berrettini visits every day for his fill of pasta bianco.

But the fun may end Friday in his first meeting with Nadal.

“I think he’s the greatest fighter ever in this sport,’’ Berrettini said.

Indeed, that is why McEnroe thinks Nadal will break Federer’s Grand Slam record of 20. A title here will give Nadal 19 slams, and he doesn’t see any reason why Nadal won’t get to 20 at the event he owns — the French Open.

“He could be at least tied with Roger next year,’’ McEnroe said. “When you look how fit he is now, no reason to think he can’t play at this level a few more years. There’s no reason both [Nadal and Novak Djokovic] can’t pass Federer. I don’t say it’s out of the realm of possibility Roger can win another one. But certainly, it’s not going to get any easier when you look at how good those two are playing.”

This would be Nadal’s fourth Open. He won the hard-court event in Montreal last month. “Nobody thought he’s a hard-court specialist,’’ McEnroe said. “[Nadal] looks better right now than at any time on hard court.”

The other semifinal pits the tour’s Russian meteor, No. 5 Daniil Medvedev, who has rankled fans here, and No. 78 Grigor Dimitrov, the Federer slayer. Their head-to-head stands at 1-1.

McEnroe is picking Dimitrov in an upset based on Medvedev’s shaky health (quadriceps, shoulder). He’s played a slew of matches in making three finals this summer.

“Certainly he’s not 100 percent physically,’’ McEnroe said. “I can see him coming out tired in the semis. Dimitrov. the way he played Federer, he’s very athletic and outlasted him. He’s a great defender.

“I give a slight edge to Dimitrov. He was one of the guys we looked at as a perennial top-10 player. He just lost his game the last 18 months, but he’s refound it.”