Last year's runner-up Madison Keys is through to the quarter-finals of the US Open after she defeated 29th seed Dominika Cibulkova 6-1 6-3.
American 14th seed Keys broke twice in the first set and again on Cibulkova's first game in the second.
She dropped serve shortly afterwards but broke back twice to win in one hour and 16 minutes on Arthur Ashe.
Keys will face the winner in the match between Maria Sharapova and Carla Suarez Navarro in the quarter-final.
She said: "I am glad I got the win and can come out here again for another match.