Third seed Jessica Pegula left the court in tears after a frustrating US Open fourth-round defeat by American compatriot Madison Keys.
Pegula had been one of the favourites for the title but put in a poor performance in a 6-1 6-3 defeat.
Despite her success on the WTA Tour, the 29-year-old has yet to go beyond the quarter-finals at any Grand Slam.
Keys, runner-up in New York in 2017, will face Wimbledon champion Marketa Vondrousova next.
Pegula won the Canadian Open in the build-up to the final major of the year, registering a notable victory over top ranked Iga Swiatek in the process.