Best seed Iga Swiatek recovered to defeat unseeded Jule Niemeier and go to her first quarterfinal in New York, preventing a US Open shock.
Swiatek was down a set and a break before returning to defeat the German 2-6 6-4 6-1.
The top WTA player this year has been the Polish player, age 21, who is going for a seventh championship in 2022.
The current French Open champion will face Jessica Pegula of America, who defeated Petra Kvitova of the Czech Republic, the 21st seed.
Later on Monday, Victoria Azarenka, a three-time finalist, was defeated in three sets by Czech 22nd seed Karolina Pliskova, advancing her to the round of eight.
With a victory against the Belarusian, Pliskova—a semifinalist at the US Open in 2016—achieved her second straight quarterfinal appearance.
She will compete against sixth-seeded Belarusian Aryna Sabalenka, who defeated American Danielle Collins (seed 19) 3-6 6-3 6-2 after rallying from a set down.
Following Ashleigh Barty’s unexpected retirement in March, Swiatek assumed the top spot, and she more than earned it by going on a 37-match winning run.
Six titles were won in a row due to her dominance; she won in Doha, Indian Wells, Miami, Stuttgart, and Rome before adding her second career victory at Roland Garros.
She has, predictably, been unable to maintain that very high level, but up until Niemeier, 23, grabbed the lead, she had not lost a set in New York.
The Wimbledon quarterfinalist Niemeier was able to threaten a significant upset and continue her breakthrough season with a notable victory thanks to Swiatek’s numerous errors in the first set and the first few games of the second.
However, the German started making errors at crucial moments, especially double faults, and Swiatek gradually improved to outperform his fourth-round performance at Flushing Meadows last year.
Swiatek said, “I’m happy I just didn’t lose hope.”
“In the first set, she played incredibly well, and in the second, I tried to pay attention to the little details that make up our foundation. I’m glad I stayed on my feet.”