US Open: Coco Gauff progresses to fourth round while compatriots Taylor Fritz, Amanda Anisimova, Madison Keys knocked out

Gauff, US Open champion in 2023, was facing world No 40 Cristina Bucsa, and though far from her best, did enough to grind out a 6-3 6-4 success to progress to the last 16.

The 22-year-old will next face the winner of compatriot Iva Jovic vs the Philippines's Alexandra Eala for a quarter-final spot.

"I think it was way different playing in the day than at night. Once I was down that break I just told myself I need to accelerate through my shots," Gauff said.

"She's a tricky player and sometimes she can pick it up and slow it down, so it was tough for me to get a rhythm but I'm just happy with how I fought through even when I wasn't playing my best."

Yet, the American charge faltered badly at Flushing Meadows after stunning defeats for Fritz, Keys and Anisimova.

Fritz, the ninth seed, looked to be cruising into the fourth round when he moved two sets ahead of Argentina's Federico Cerundolo.

The 28-year-old, runner-up two years ago, had not dropped a set all week and appeared to be on the verge of joining compatriots Ben Shelton, Frances Tiafoe, Tommy Paul and Alex Michelson in the last 16.

But Cerundolo, the surprise winner at Queen's Club earlier this summer, scrapped his way back into an error-heavy match and won 3-6 4-6 6-3 6-4 6-4.

The host nation is still looking for its first men's singles title winner since 2003, when Andy Roddick beat Juan Carlos Ferrero in the final.

Paul, the 20th seed, takes on Carlos Alcaraz in what should be a first genuine test of the defending champion's title credentials following his return from injury.

"I think I played Carlos more than anybody on tour, for me, which is kind of crazy," he said. "We've had some good matches.

"But, I mean, he's the test, him and (Jannik) Sinner. They have been playing great, and I guess Carlos we haven't really seen too much, but he's obviously doing pretty well coming right back to competition."

Elsewhere, Belgian 28th seed Alexander Blockx stunned Italian fifth seed Flavio Cobolli 6-7 (4-7) 6-3 ‌6-0 6-3 to advance to the fourth round, where he will meet Argentina's ​24th-seeded Cerundolo.

Zheng stuns to knock out Keys after latter led 5-0 in third set

Keys, the 2017 runner-up, was crestfallen after blowing a healthy lead to lose 1-6 7-6 (7-3) 7-5 to China's Qinwen Zheng.

The 31-year-old said: "I feel like I obviously got off to a really good lead, and then I just got really scared, like I couldn't swing.

"I don't know. Tennis just feels really hard right now, so I feel like that kind of took over."

Last year's beaten finalist Anisimova hit 46 unforced errors in a 6-2 7-5 defeat by Austrian Anastasia Potapova.

French Open champion Mirra Andreeva beat Czech Nikola ​Bartunkova 6-2 7-6 (7-5) to advance to the fourth round at the US Open for the first time. The Russian fifth seed next faces Potapova.

Six-time Grand Slam champion Iga Swiatek dug deep to defeat Czech 25th seed Marie Bouzkova 7-6 (7-3) 7-6 (7-3) and reach ‌the fourth round. The eighth-seeded Pole will next face Qinwen.

Meanwhile, Serena and Venus Williams escaped a fine for not talking to the media after their defeat in the doubles on Friday night.

The superstar sisters were beaten in three tight sets by Maya Joint and Chan Hao-ching in their first match at Flushing Meadows in four years.

Players are usually fined for not fulfilling their media duties, but it is understood the Williams' will not be punished.

The US Open is live on Sky Sports from August 30. Stream tennis with no contract on NOW and the Sky Sports App . You can also watch the Laver Cup at The O2 in London from 25-27 September live on Sky Sports.