World number one Iga Swiatek became the first Polish woman to reach the US Open quarter-finals on Monday when she defeated Jule Niemeier in an error-strewn last-16 clash.
French Open champion Swiatek recovered from a set and a break down to see off her 108th-ranked German opponent, 2-6, 6-4, 6-0.
Top seeded Swiatek will face US eighth seed Jessica Pegula for a place in the semi-finals.
In a mistake-riddled clash on Louis Armstrong Court, there were a total of 15 double faults, 12 breaks of serve and 76 unforced errors.
"It's really satisfying. This is my first quarter-final in New York so I am really proud of it," said Swiatek.
Wimbledon quarter-finalist Niemeier hadn't won a hardcourt match in her career before coming to New York.
However, went into Monday's match not having dropped a set and fired up to repeat her Wimbledon journey where she had also beaten world number two Anett Kontaveit.
sabalenka wins
Aryna Sabalenka reached the US Open quarter-finals for a second successive year with a three-set comeback win over Danielle Collins.
The world number six from Belarus triumphed 3-6, 6-3, 6-2 over her American opponent who she has now beaten in New York three times in the last five editions.
Sabalenka eventually fell at the semi-finals in 2021 and her 2022 bid looked in danger on Monday when she needed a medical time-out to treat a leg injury.
However, she eventually fought back from a set down against the Australian Open runner-up and sealed victory on the back of a double break in the decider.
Pegula into last 8
Jessica Pegula became the second American woman into this year's US Open quarter-finals after brushing aside two-time Grand Slam champion Petra Kvitova in straight sets.
The 28-year-old eighth seed shrugged off a rain delay on the Arthur Ashe Stadium court to win 6-3, 6-2 and ease into a last eight meeting with either world number one Iga Swiatek.
Pegula, whose parents are the billionaire owners of the Buffalo Bills NFL franchise, was always in control against out-of-sorts Czech veteran Kvitova, who had taken down Spain's Garbine Muguruza in the third round.
Pegula has reached quarter-finals at the Australian Open and French Open this season but had never gone further than the third round in five previous appearances at the US Open. She joins fellow American Coco Gauff in the last eight.