NEW YORK — Matteo Berrettini reached the U.S. Open semifinals after nearly four exhausting hours, overcoming some nervous moments at the end to outlast Gael Monfils 3-6, 6-3, 6-2, 3-6, 7-6 (5) on Wednesday.

The 23-year-old Italian finally closed it out on his fifth match point — long after he double-faulted away his first chance — after 3 hours, 57 minutes.

"One of the best matches I ever saw. I was playing, but I was watching, also," Berrettini said with a smile.

It started under muggy conditions and finished with the roof closed at Arthur Ashe Stadium after rain arrived during the third set.

The short break seemed to benefit Monfils, who is 10 years older and had been leaning on his racket or wiping sweat off his legs between points. He won the fourth set but didn't have enough left at the finish of a match that took 68 minutes to play the final set.

The 24th-seeded Berrettini advanced to his first Grand Slam semifinal, where he will face No. 2 Rafael Nadal or No. 20 Diego Schwartzman. He became only the second Italian to reach the final four of the U.S. Open, following Corrado Barazzutti in 1977.

He could've done it more easily, but double-faulted for the first time in the match with a weak second serve into the net on his first match point at 5-4.

"I was like this, a little bit tight," he said during his postmatch interview.

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Belinda Bencic also reached her first Grand Slam semifinal, wearing down Donna Vekic for a 7-6 (5), 6-3 victory.

A day after Roger Federer and Stan Wawrinka departed the U.S. Open on the same day, Bencic did her part to lift some of spirits in Switzerland.

"It would be really nice if the boys could also make it to semifinals," she said, "but I'm happy I can kind of do it for them and don't let them down."

Coming off her upset of top-ranked Naomi Osaka in the fourth round, the 12th-seeded Bencic kept up her big hitting and broke open a close match midway through the second set by winning eight straight points.

Trailing 3-2 in the set, that sent her into the lead and Vekic never recovered, with Bencic winning the final four games to surpass her 2014 run to the U.S. Open quarterfinals for her best performance in a major tournament.

"Even when you are playing bad, you want to come back to this feeling. You want to eventually get the big wins and have these nice feelings," said Bencic, who has battled injuries in the five years since.

Bencic advanced to play either No. 15 Bianca Andreescu or No. 25 Elise Mertens on Thursday night. Six-time U.S. Open champion Serena Williams faces fifth-seeded Elina Svitolina in the other semifinal.

One men's semifinal is already set, with No. 5 Daniil Medvedev facing Grigor Dimitrov, who eliminated five-time U.S. Open champion Federer on Tuesday. Wawrinka had beaten top-ranked Novak Djokovic, the defending champion, in the fourth round before losing to Medvedev.

Vekic, seeded 23rd, was also seeking her first semifinal in a major tournament. But with her face bright red as the sun beat down on Arthur Ashe Stadium, she couldn't keep up with her friend's power during the biggest moments of the match.

"I think she was just playing better tennis overall today," Vekic said. "I felt like I couldn't get three good points together. I was, like, playing one point good, then bad."

It was Bencic who cracked first, missing an easy putaway on game point while serving at 4-all in the first set. She momentarily seemed to lose focus, as Vekic then won the next three points to break for a 5-4 lead.

But Bencic broke right back to even it again and eventually they headed to a tiebreaker, where the 22-year-old Bencic has thrived this season. Trailing 2-1, she ran off five of the next six points before eventually wrapping it up to improve to 10-2 in tiebreakers this season.

Vekic recovered to take a 3-2 lead in the second set, but that 10-point fifth game seemed to take a little out of her, with Bencic running off the next eight points to seize the lead.

Nadal, who has won three of his 18 major titles at Flushing Meadows, will be playing in his 40th career Grand Slam quarterfinal. He is 7-0 against Schwartzman.

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