New York - Last year's runner-up Madison Keys returned to the US Open quarter-finals on Monday with a 6-1, 6-3 win over Slovakia's Dominika Cibulkova.
American 14th seed Keys, who was defeated by compatriot Sloane Stephens in the 2017 championship match, fired 25 winners to Cibulkova's seven.
The 23-year-old will face either former champion Maria Sharapova or Spain's Carla Suarez Navarro for a place in the semi-finals.
"I am really glad I got the win," said Keys after reaching her third Grand Slam quarter-final of the season.
"Dominika is a good player so even though I was a set and 2-0 ahead, it wasn't surprising that she would come back and win a few games.
"So I just had to focus on getting some first serves in and wait for the right ball."
US Open results on Monday, the eighth day of the 2018 tournament at Flushing Meadows (x denotes seeded player):
Kei Nishikori (JPN x21) bt Philipp Kohlschreiber (GER) 6-3, 6-2, 7-5
Madison Keys (USA x14) bt Dominika Cibulkova (SVK x29) 6-1, 6-3