New York - Rafael Nadal ramped up his quest for a fourth US Open title on Monday with an impressive win over 2014 champion Marin Cilic to advance to the quarter-finals while Alexander Zverev slumped to a four-set defeat.
Second seed Nadal - the winner at Flushing Meadows in 2010, 2013 and 2017 - produced some electrifying moments of brilliance to end the challenge of Croatian 22nd seed Cilic 6-3, 3-6, 6-1, 6-2.
After barely breaking a sweat in reaching the last 16, a run that included a second-round walkover, Nadal stared down his stiffest test so far to surge into a quarter-final meeting with Argentine 20th seed Diego Schwartzman.
The Spaniard exchanged the first two sets with Cilic but grasped control by breaking for 3-1 in the third, a series of dazzling winners drawing an animated fist-pump from golf legend Tiger Woods at Arthur Ashe Stadium.
Nadal reeled off nine games in succession across the third and fourth sets and 12 of the final 15 to nail down a 40th Grand Slam quarter-final appearance, nine of which have come at the US Open.
"The emotions I have when I play here are impossible to describe. I love the sport and feel very lucky to still be playing tennis here. Eight years ago I didn't think that would happen as my body was suffering badly," Nadal said.
"It's a huge honour playing in front of all of you and playing in front of Tiger is a very special thing. I always say I don't have big idols but one idol is him and I always try to follow him."
Nadal's path to the final sees him take on Schwartzman next after the 5-foot-7 (1.70m) Argentine chopped down sixth seed Zverev.
"He is playing amazing, nothing new, he's one of the players with best talent on tour," the 18-time Grand Slam champion said of his upcoming opponent.
"It will be a big challenge. I have to play my best. I'm happy for him. He's a close friend and I hope to play a great match."
Zverev rolled through the opening set against Schwartzman under the roof on Ashe during a rainy afternoon session, but he lost his way to go down 3-6, 6-2, 6-4, 6-3.
The German was enjoying his deepest run in New York but committed 17 double faults and 65 unforced errors and received a point penalty for swearing as Schwartzman advanced to a second US Open quarter-final in three years.
"Generally my season so far has not been the best," said Zverev, who has reached just two quarter-finals in 18 Grand Slam appearances.
Zverev said he was hindered a "very swollen" back and right hip following a fall in his previous match.
"I had a lot of chances which I didn't use early in the match. He kind of ran away with it."
Zverev lost his serve three times during the second set but appeared to have steadied himself when he moved a break ahead at 3-2 in the third, only for Schwartzman to wrest the momentum back in his favour after a lengthy sixth game.
"It was tough because I was feeling I had the chance to win this and I had a few break points I could not take," Schwartzman said. "He was up a break and then I recovered really quickly and I felt great after that."
Matteo Berrettini became just the second Italian man to progress to the US Open quarter-finals, 42 years after Corrado Barazzutti's run to the last four in New York.
Berrettini, the 24th seed, eased to a 6-1, 6-4, 7-6 (8/6) win over Russia's 43rd-ranked Andrey Rublev to reach the last eight at a Grand Slam for the first time.
"It's something really crazy. I cannot believe it right now. I need a few hours to understand what happened," said Berrettini, 23, who goes on to play French 13th seed Gael Monfils.
"I'm just happy. Seeing my team and family here and crying, for me it's unbelievable."
Berrettini went one step further than his run to the last 16 at Wimbledon in July, where he was beaten by Roger Federer.
Monfils, a 2016 US Open semi-finalist, crushed the 33-year-old Andujar's bid to become the oldest player in the Open era to reach his first Grand Slam singles quarter-final with a 6-1, 6-2, 6-2 rout.
US Open results on Monday (x denotes seeding):
Matteo Berrettini (ITA x24) bt Andrey Rublev (RUS) 6-1, 6-4, 7-6 (8/6)
Gael Monfils (FRA x13) bt Pablo Andujar (ESP) 6-1, 6-2, 6-2
Diego Schwartzman (ARG x20) bt Alexander Zverev (GER x6) 3-6, 6-2, 6-4, 6-3
Rafael Nadal (ESP x2) bt Marin Cilic (CRO x22) 6-3, 3-6, 6-1, 6-2
Belinda Bencic (SUI x13) bt Naomi Osaka (JPN x1) 7-5, 6-4
Donna Vekic (CRO x23) bt Julia Goerges (GER x26) 6-7 (5/7), 7-5, 6-3
Bianca Andreescu (CAN x15) bt Taylor Townsend (USA) 6-1, 4-6, 6-2
Elise Mertens (BEL x25) bt Kristie Ahn (USA) 6-1, 6-1