NEW YORK (AP) — Matteo Berrettini describes his mental coach as a big help and a best friend. They’ve been speaking on the phone before and after every match during Berrettini’s run to his first Grand Slam semifinal.

They had plenty to chat about when it came to this latest victory.

Berrettini, a 23-year-old from Rome, gave Italy a spot in the final four at the U.S. Open for the first time since 1977 in dramatic fashion, double-faulting away his initial match point and then needing four more to finally put away 13th-seeded Gael Monfils of France 3-6, 6-3, 6-2, 3-6, 7-6 (5) after nearly four hours in Arthur Ashe Stadium on Wednesday.

Monfils finished with 17 double-faults but managed to avoid any throughout the entire, exhausting fifth set until he served at 6-5 — and then he had three in that game, plus another two in the deciding tiebreaker, often doubling over between points to rest and catch his breath.

“A very bad day for me, serving,” Monfils said.

Berrettini acknowledged the obvious afterward, too, saying he felt “a little bit tight.”

You think?

It all was a bit of a whir.

“Right now, I don’t remember any points, just the (last) match point, you know?” he said. “I remember also the double-fault; I have to be honest.”

Berrettini, who is seeded 24th, will get a day to recuperate: He will face No. 2 Rafael Nadal or No. 20 Diego Schwartzman in the semifinals Friday.

The other men’s semifinal that day is No. 5 Daniil Medvedev against unseeded Grigor Dimitrov, who beat an injured Roger Federer in five sets on Tuesday night to become, at No. 78, the lowest-ranked semifinalist at the U.S. Open since 1991.

Berrettini-Monfils began on a muggy afternoon and concluded with Ashe’s retractable roof shut after rain came during the third set.

Monfils, who is 10 years older, fell to 2-7 in major quarterfinals and could be forgiven for wondering how many more chances he’ll get.

Berrettini, meanwhile, is on top of the world at the moment. With Corrado Barazzutti, Italy’s only other male semifinalist at the U.S. Open, back in 1977, in the stands Wednesday, Berrettini used his big forehand to produce 24 winners.