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. Last week in Cincinnati, Gauff said she's practicing patience on tour the rest of the season.

Tennis star Coco Gauff hired biomechanics expert Gavin MacMillan, who previously helped world number one Aryna Sabalenka improve her serve.

American tennis player Coco Gauff has parted ways with one of her coaches Matt Daly and brought on biomechanics expert Gavin MacMillan.