The most memorable image of a terrific match had nothing to do with the tennis: As the clock hit midnight after the second set, Townsend jumped rope on the sideline while waiting for Andreescu to return from a bathroom break.
The 15th-seeded Andreescu's big returns and pinpoint passing shots dominated the opening set, but Townsend adjusted in the second, waiting a bit before picking her spots to head to the net. This was the fourth-round Slam debut for both. Each eliminated a former No. 1 and major champion along the way. Andreescu beat Caroline Wozniacki, while the 116th-ranked Townsend got past Simona Halep.
The 19-year-old Andreescu faces No. 25 Elise Mertens of Belgium for a spot in the semifinals.
Rafael Nadal easily passed his first test of this year's U.S. Open and reached the quarterfinals at a ninth consecutive Grand Slam tournament.
With Tiger Woods throwing uppercuts in the stands, Nadal shook off dropping a set and powered past 2014 champion Marin Cilic 6-3, 3-6, 6-1, 6-2 in the fourth round.
Nadal dropped a set for the first time in this year's tournament but quickly responded by breaking to lead 3-1 in the third set and was on his way.
Nadal is seeking his fourth title at Flushing Meadows and his 19th Grand Slam trophy overall. Roger Federer holds the men's record of 20; they only could meet in the final this year. The rivals never have played each other in New York.
The No. 2-seeded Nadal, who retired from his 2018 semifinal at the U.S. Open with a knee injury, will try to get back to the final four by beating No. 20 Diego Schwartzman.
Gael Monfils quickly advanced to his third U.S. Open quarterfinal, needing less than an hour and a half to dispatch Pablo Andujar 6-1, 6-2, 6-2.
Monfils, the No. 13 seed from France, was never seriously threatened against the 70th-ranked Andujar, ripping 34 winners to just four from his opponent and never losing his serve.
For the 33-year-old Monfils, Flushing Meadows gives him another chance to deliver on the potential of one of the game's great shotmakers and showmen. Though he has now advanced to at least the quarterfinals of nine Grand Slam tournaments, he has never gone further than his semifinal showings at Roland Garros in 2008 and the U.S. Open in 2016.
Monfils next takes on No. 24 Matteo Berrettini, who earlier defeated Andrey Rublev in straight sets.
Coco Gauff's run at the U.S. Open is over.
Two days after she broke down in tears after a straight-set singles loss to top-ranked Naomi Osaka, Gauff and doubles partner Caty McNally fell in the third round to the eighth-seeded team of Victoria Azarenka and Ash Barty 6-0, 6-1.
They can take at least one positive from the drubbing: Team McCoco — 15-year-old Gauff and 17-year-old McNally — was one of the biggest crowd favorites of the U.S. Open. They once again drew a near-capacity crowd for their match, this time on the Grandstand court.
Azarenka and Barty move on to a quarterfinal matchup against the top-seeded team of Timea Babos and Kristina Mladenovic.
Elise Mertens cruised into her first appearance in the U.S. Open quarterfinals with a 6-1, 6-1 victory over American wild card Kristie Ahn.
Mertens, the No. 25 seed from Belgium, needed a mere 67 minutes dismiss the 141st-ranked Ahn, a 27-year-old American who had become the comeback story of the tournament with an 11-year gap between Flushing Meadows appearances.
Mertens hit 17 winners and took advantage of 25 unforced errors from her opponent.
For Mertens, it's her second-best showing in a Grand Slam event, after reaching the semis of the Australian Open last year.
She moves on to play the winner of the match later Monday between American qualifier Taylor Townsend and 15th-seeded Bianca Andreescu.
Sixth-seeded Alexander Zverev doubled-faulted 17 times on his way out of the U.S. Open. Diego Schwartzman took full advantage in beating him 3-6, 6-2, 6-4, 6-3 to advance to the quarterfinals at Flushing Meadows for the second time.
Zverev's serving problems have dogged him for months and they came back in force against Schwartzman. The lanky German lost his serve eight times, won just 32 percent of second-serve points and amassed 65 unforced errors. He also was hit with a point penalty for swearing in the final set to put Schwartzman up 5-2.
The 20th-seeded Schwartzman, meanwhile, went about his steady baseline and retrieving game, taking the majority of long rallies in a match when some points went on for as many as 35 strokes.
The Argentine, who previously reached the quarterfinals at the French Open last year and Flushing Meadows in 2017, next takes on the winner of the match later between second-seeded Rafael Nadal and No. 22 Marin Cilic.
Matteo Berrettini overpowered Andrey Rublev 6-1, 6-4, 7-6 (6) to become the first Italian man in the U.S. Open quarterfinals since 1977.
Berrettini, the No. 24 seed from Italy, relied on a strong service game and some well-timed drop shots to overcome Rublev, who had taken out the volatile Nick Kyrgios and No. 8 Stefanos Tsitsipas.
Berrettini won 14 of his 15 service games and more than 80 percent of his first-serve points, and he ripped 37 winners, including a deftly angled volley on match point to close it out.
It's his deepest run at a Grand Slam event after reaching the fourth round at this year's Wimbledon. Berrettini became the first Italian man in the U.S. quarterfinals since Corrado Barazzutti 42 years ago.
Next up for Berrettini is the winner of the match later Monday between 13th-seeded Gael Monfils and Pablo Andujar.
Matches have started on some of the outer courts at the U.S. Open after rain delayed much of the early play.
Only matches at Arthur Ashe Stadium and Louis Armstrong Stadium, which both have retractable roofs, were able to be played as scheduled until the early afternoon.
But a few outer courts are now opened and hosting play, including the Grandstand where Coco Gauff and Caty McNally were scheduled to play their third-round doubles match.
Donna Vekic survived a match point to beat Julia Goerges 6-7 (5), 7-5, 6-3 and advance to the U.S. Open quarterfinals, her deepest run in any Grand Slam.
Vekic, the No. 23 seed from Croatia who lost to Goerges at this stage in last year's Open, had to dig out of a hole to beat the No. 26-seeded German this time. Vekic was down 5-4 in the second set and faced a match point against her, but Goerges failed to close it out in a service game in which she double-faulted three times.
In the deciding set, Vekic made a crucial service break to go up 5-3 and closed out the match when she put up a lob that Goerges slammed long.
Next up for Vekic is No. 13 Belinda Bencic, who upset top-seeded Naomi Osaka 7-5, 6-4 earlier on Arthur Ashe Stadium. Vekic beat Bencic in the third round of this year's French Open.
Defending champion Naomi Osaka was eliminated from the U.S. Open in the fourth round with a 7-5, 6-4 loss to No. 13 Belinda Bencic.
Osaka, who struggled with left knee pain before the tournament, was visited by medical personnel in the second set and took some type of tablet, but it was unclear what was bothering her.
The top-ranked Osaka, who looked so sharp in the second set of her 6-3, 6-0 rout of 15-year-old Coco Gauff on Saturday night, didn't seem to have the same movement or spirit in the first match on Arthur Ashe Stadium on Monday.
Play is being delayed on all the outside courts at the U.S. Open because of rain.
Tournament officials announced that play would not begin before 12:30 p.m. on any of the outside courts.
So the only match going on at that point was a fourth-round women's singles meeting between No. 23 Donna Vekic and 26th-seeded Julia Goerges at Louis Armstrong Stadium, which has a retractable roof. Play was scheduled to begin on Arthur Ashe Stadium, the other roofed stadium, at noon with top-ranked Naomi Osaka facing No. 13 Belinda Bencic.
After an easy first week at the U.S. Open, Rafael Nadal figures to have a challenge in the fourth round.
The No. 2 seed faces No. 22 Marin Cilic in a matchup of past champions, with the winner getting a spot in the quarterfinals.
Nadal has played just two matches and spent a little more than four hours on the court, getting a walkover in the second round and winning twice in straight sets.
Cilic, the 2014 champion, hopes to improve to 6-0 in fourth-round matches at Flushing Meadows.
Top-ranked Naomi Osaka is also in action, while American teenagers Coco Gauff and Caty McNally try to remain unbeaten in doubles. Taylor Townsend and Kristie Ahn of the U.S. hope to extend their longest runs in Grand Slam tournaments.
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