Gauff has not appeared confident with her serve since beating Aryna Sabalenka on clay earlier this summer. She won three matches in the US Open tuneup earlier at the Cincinnati Open, but lost to Italy's Jasmine Paolini in the fourth round.

Coco Gauff has fired a member of her coaching staff, Matt Daly, days ahead of the start of the US Open. She's replaced him with Gavin MacMillan, a biomechanics specialist who's credited with having helped Aryana Sabalenka fix her serve and rise to the No.