Jessica Pegula ousted top seed Iga Swiatek in the quarterfinals to continue the rich vein of her compatriots’ success at the US Open while men’s world number one Jannik Sinner beat Daniil Medvedev to book his spot in the semifinals.

Pegula took advantage of an error-strewn performance from Swiatek to enter her maiden Grand Slam semifinal in straight sets (6-2 6-4), while Sinner prevailed 6-2, 1-6, 6-1, 6-4 to reach the last four at Flushing Meadows for the first time on Wednesday.

The losses for Swiatek and Medvedev ensured that the US Open will crown two new champions this year.

Sinner will face Jack Draper for a spot in a second Grand Slam final after the United Kingdom’s surprise package earlier stunned hobbled Australian Alex de Minaur 6-3, 7-5, 6-2 to become the first British man to reach the semis since 2012.

Pegula, who had lost six previous Grand Slam quarterfinals, will take on Karolina Muchova after the unseeded Czech beat Brazilian Beatriz Haddad Maia 6-1, 6-4 in the day session at Arthur Ashe Stadium despite battling a “bug”.

“I’m really happy to be through to the semifinals,” said Pegula, who joined male compatriots Taylor Fritz and Frances Tiafoe at the business end of the tournament.

“I thought I played a really clean match. I feel like I didn’t really do anything that bad, and was able to kind of jump on her really early and I think frustrate her.”

Home favourite Pegula has been cheered on by several celebrities and former champions during her journey at this year’s US Open and the latest star in stands was celebrated American gymnast Simone Biles.

Swiatek, the 2022 champion, could not claim the same as she suffered service issues in the opening set and made 41 unforced errors over the match.

The Pole’s struggles with her serve started early and Pegula took full advantage to race out to a 4-0 lead in the first set.

Swiatek looked sharper as she broke Pegula early in the second set but was unable to regain momentum with the sixth seeded American breaking back and going on to take the win.

“I didn’t really understand why my serve wasn’t working,” Swiatek lamented.

“It was hard for me to find, like, a proper solution for that. Today I just made too many mistakes.”

Olympic gold medallist Simone Biles waves during a break in a match between Jessica Pegula and Iga Światek [Eduardo Munoz Alvarez/AP]

Mistakes also plagued 2021 champion Medvedev, who made 57 unforced errors over a topsy-turvy match against top seed Sinner.

The Russian failed to capitalise on the momentum he gained by winning the second set, losing five games straight in the third before handing Sinner a break in the fourth with an unforced error.

“It was strange the first two sets because whoever made the first break started to roll,” said Sinner, who beat Medvedev in the Australian Open final this year before losing to him in the Wimbledon quarterfinals.

“It was very tough… we knew it would be very physical,” Sinner added.

Jannik Sinner dropped one set against former US Open champion Daniil Medvedev during their quarterfinal quarterfinals [Adam Hunger/AP]

Draper powered into his first Grand Slam semifinal without having dropped a set in the tournament and earned his first career victory over 10th seed De Minaur.

The Australian battled to find his range from the start and was broken early, setting the tone for the match as he racked up the unforced errors.

The Australian broke to level the second set at 4-4 only to see Draper break in the 11th game before consolidating to seize a 2-0 lead in the match.

Draper’s power and precision in the third set wore down De Minaur, who has been struggling with a hip issue since Wimbledon.

“The way he can spread the court, being a lefty and really move you around the court, it takes a toll on the body,” De Minaur said. “Accumulation of matches takes a toll as well.”

Not since Andy Murray won the title in 2012 has the UK had a representative in the men’s singles semifinals at the US Open.

“I feel the best fitness-wise I’ve been in a long, long time and I think that’s where Alex has sort of got me in the past,” said Draper.

In the day’s opening match, Muchova continued her renaissance after a long injury layoff in the wake of an operation on a wrist injury she sustained last year at Flushing Meadows.

In only her sixth tournament back on tour, Muchova looked sharp early on as she grabbed a 4-0 lead over Haddad Maia before taking the opening set.

The Brazilian improved in the second set and the players exchanged breaks before Muchova, after having the physio and doctor at her chair, held to reach 5-3 before taking advantage of new balls and sealing victory with an ace.

“I played good in the key points, meaning when I had a breakpoint or I was serving for a game, I always pulled out a good shot,” Muchova said.