American tennis star Coco Gauff has parted ways with her coaches Matt Daly and J.C. Faurel and brought on biomechanics expert Gavin MacMillan, according to multiple reports.

Gauff, 21, who has struggled with her serve since her first-round defeat at Wimbledon last month, made the coaching shift days before the start of the first round at the U.S. Open.

MacMillan previously worked with current world No. 1 Aryna Sabalenka to fix her serve and founded the Sport Science Lab — a company that specializes in sports performance, physical rehabilitation and general fitness.

Coco Gauff in action against Jasmine Paolini of Italy in the quarter-final on Day 9 of the Cincinnati Open at Lindner Family Tennis Center on August 15, 2025 in Mason, Ohio Getty Images

MacMillan was on the court as Gauff

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