Wimbledon champion Angelique Kerber was knocked out of the US Open on Saturday, losing 3-6, 6-3, 6-3 to Slovakia's Dominika Cibulkova who admitted the German had "killed" her in two previous meetings this year.
Fourth seeded Kerber, the 2016 champion in New York, had been bidding to become just the third woman in the last 20 years to win Wimbledon and the US Open in the same year.
Cibulkova, the 29th seed who made the quarter-finals in 2010, will face 2017 US Open runner-up Madison Keys for a place in the last-eight.
"I played Angie twice this year (Sydney and Eastbourne) and she killed me on court even though I wasn't playing that bad," said 29-year-old Cibulkova.
"This time I did a few different things and it worked.
"I lost the first set today but I knew that if I just kept doing what I was doing it would come."