Third seed Jessica Pegula and Wimbledon finalist Ons Jabeur suffered frustrating defeats in the fourth round at the US Open.
American Pegula, who had been one of the favourites for the title, put in an error-strewn performance in a 6-1 6-3 loss to compatriot Madison Keys.
Despite her success on the WTA Tour, the 29-year-old has yet to go beyond the quarter-finals at any Grand Slam.
Last year’s runner-up Jabeur lost 6-2 6-4 to China’s Zheng Qinwen.
Qinwen, 20, reached the first Grand Slam quarter-final of her career and will face Belarusian second seed Aryna Sabalenka next.
Sabalenka, a semi-finalist at Flushing Meadows in 2021 and 2022, won 6-1 6-3 against Russian 13th seed Daria Kasatkina.
The Australian Open champion, 25, will be become the new world number one at the end of the tournament following Iga Swiatek’s exit in the last 16.
“I had no doubt that Iga was going to make it to the final. I was sad that she lost, but becoming number one means a lot to me,” said Sabalenka.
“I’ve been pushing myself a lot this year to make this goal and I still can’t believe it, but I didn’t want to be distracted for tonight.”
Jabeur unable to find ‘warrior’ mood
Jabeur was left heartbroken after losing a second Wimbledon final in July and has struggled with illness during her time in New York.
The Tunisian fifth seed has also exerted a lot of energy on the court, having won both of her previous two matches in three sets.
Jabeur was broken twice in the first set against Qinwen, rescuing one of them before handing the momentum straight back to her opponent.
She saved four match points in the second as Qinwen’s nerves struck, but the Chinese 23rd seed held on to secure a place in the last eight.
“No matter what the tournament is, you always take a great lesson,” said 29-year-old Jabeur.
“I know that I can dig deep. Maybe I’m tough with myself today because I couldn’t get that warrior mood on. It’s just disappointing.”