Coco Gauff, 16, beats No 2 seed Aryna Sabalenka to reach Lexington quarters

American teenager Coco Gauff overcame some shaky serving Wednesday to beat No. 2 seed Aryna Sabalenka 7-6 (2), 4-6, 6-4 and reach the Top Seed Open quarterfinals with her third career victory over a top-15 opponent.

The 16-year-old Gauff hit 10 double-faults and was broken seven times.

I guess, she said afterward, everything was an A but the serving.

But she hung in there with steady baseline play against the hard-hitting Sabalenka, who had 14 double-faults, including four in one game.

It was a topsy-turvy match that lasted nearly three hours and featured a bit of confusion when Gauff and her father, Cori, got into a discussion with the chair umpire about what sort of coaching is allowed under new rules the WTA put in place recently.