Defending champion Sloane Stephens beat two-time Grand Slam champion Victoria Azarenka 6-3 6-4 to reach the third round of the US Open in New York.
The American third seed broke twice in the first set and three times in the second at the Arthur Ashe Stadium.
Both players battled hard in the second set and Azarenka came from 3-1 down to lead 4-3 before the roof was closed.
The 25-year-old French Open finalist will face Belgium 15th seed Elise Mertens in the next round.
It was Belarusian Azarenka's first appearance at the US Open for three years.