World number one Iga Swiatek came out on top in a meeting of Grand Slam champions as she beat Sloane Stephens to reach the US Open third round.
Swiatek will next face American Lauren Davis who beat 28th seed Ekaterina Alexandrova 0-6 6-4 7-6 (10-5).
Eighth seed Jessica Pegula and three-time finalist Victoria Azarenka also advanced on day four in New York.
Swiatek has won 52 matches this year, including a 37-match winning streak that included her French Open title win.
However, she has not gone beyond the quarter-final stage of a tournament since losing in the third round at Wimbledon in July.