NEW YORK — Iga Swiatek and Daniil Medvedev, the last remaining former champions in the U.S. Open singles brackets following several surprising outcomes, effortlessly advanced to the quarter-finals at Flushing Meadows on Monday.

Top seed Swiatek, who clinched the title two years ago, displayed her full range of skills in a simple 6-4 6-1 victory against Russia’s Liudmila Samsonova, beginning the evening session at Arthur Ashe Stadium. She cautioned that her level of play is set to improve further.

“Initially, it was tough to find the rhythm, particularly since we focused more on recovery than actual practice leading up to the tournament,” said Swiatek about her time in New York.

“I’m pleased that I’ve had some matches here and I definitely feel myself getting better each day.”

Earlier, Medvedev, the 2021 champion, easily overcame a fire alarm delay in the building housing the Hawkeye line-calling system to dominate Portugal’s Nuno Borge 6-0 6-1 6-3.

“It was a peculiar experience, but it actually worked in my favor since I felt like he was gaining momentum, and this disrupted that a bit,” Medvedev noted.

“However, that’s something beyond our control. Hopefully it doesn’t happen again.”

American fans had something to celebrate on their Labor Day holiday, as Jessica Pegula swiftly defeated Diana Shnaider 6-4 6-2 to reach the quarter-finals without losing a set.

The sixth seed, who sat out the French Open due to injury but recently won a tune-up event for the U.S. Open in Canada, expressed confidence in her performance.

“Today, I felt the best I had off the ground, and I intend to keep improving and bringing my top tennis for the later matches,” the 30-year-old remarked.

“There’s a lot of pressure here, but I enjoy it. It’s great being an American and receiving so much support.”

Pegula, who has made it to the quarter-finals of every Grand Slam but has never advanced further, now faces the formidable challenge of world number one Swiatek.

Karolina Muchova eliminates Jasmine Paolini

An unexpected twist early on the eighth day of the tournament occurred in the women’s draw when Karolina Muchova, a semi-finalist from last year, defeated Italian fifth seed Jasmine Paolini 6-3 6-3.

Muchova, unseeded due to a wrist injury sustained at last year’s U.S. Open that sidelined her for 10 months, showcased her talent by outpacing Paolini, who reached the finals at both the French Open and Wimbledon this year.

Muchova will next compete against Beatriz Haddad Maia, who struck 40 winners to eliminate former world number one Caroline Wozniacki with a score of 6-2 3-6 6-3.

Later at Louis Armstrong Stadium, Jack Draper became the first British man to reach the quarter-finals at Flushing Meadows since Andy Murray in 2016 with a convincing 6-3 6-1 6-2 victory over Tomas Machac.

Seeded 25th, Draper has not dropped a set throughout the tournament and will face Australian Alex de Minaur in his first Grand Slam quarter-final on Wednesday.

De Minaur secured his spot in the last eight with a hard-fought 6-0 3-6 6-3 7-5 win against compatriot and close friend Jordan Thompson.

“I have immense respect for Thommo,” said the 10th seed. “We’ve grown up together, and he’s been like a big brother to me, so I truly appreciate everything he’s done and recognize he’s a fierce competitor.”