NEW YORK - 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 at the US Open.

They'll have a lot to chat about when it comes to the Italian's latest victory.

The 23-year-old from Rome gave his homeland a spot in the final four at the US Open for the first time since 1977 on Wednesday at Arthur Ashe Stadium, 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.

"One of the best matches I ever saw. I was playing, but I was watching also," Berrettini said with a grin during his on-court TV interview.

In truth, the denouement was hardly a thing of beauty, with both men, clearly spent, fighting themselves and the tension of the moment as much as the guy on the other side of the net.

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 catch his breath.

"A very bad day for me, serving," Monfils said.

Berrettini acknowledged the obvious afterwards, saying he felt "a little bit tight".

"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, seeded 24th, will get a day to recuperate before facing No 2 Rafael Nadal in the semifinals on Friday.

The other men's semifinal 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 Open since 1991.

Nadal, the last member of the Big Three standing because Federer and Novak Djokovic are out of the draw, defeated Argentina's Diego Schwartzman 6-4, 7-5, 6-2 on Wednesday night.

That followed the last women's quarterfinal, which saw Canadian teenager and 15th-ranked Bianca Andreescu beat Germany's Elise Mertens 3-6, 6-2, 6-3.

Andreescu takes on No 13 Belinda Bencic on Thursday, while the day's other semifinal has Serena Williams against No 5 Elina Svitolina.

Like Berrettini and Medvedev, Bencic also reached her first Grand Slam semi. She followed up her upset of defending champion and No 1 seed Naomi Osaka by taking the last four games of a 7-6 (5), 6-3 victory over No 23 Donna Vekic.

"I felt like I couldn't get three good points together," Vekic said. "I was, like, playing one point good, then bad."

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

Monfils 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. With Corrado Barazzutti, Italy's only other male semifinalist at the US Open, back in 1977 looking on, Berrettini used his big forehand to produce 24 winners.

The first match point came while Berrettini served for the win at 5-3 in the fifth.

Two more came and went when Monfils served at 6-5. A fourth was erased by an ace by the Frenchman in the tiebreaker. But on the fifth, Berrettini's serve was returned long by Monfils.

Berrettini stared at the ball as it descended, making sure it landed out to confirm victory.

Associated Press