American tennis star Coco Gauff makes major change just days before US Open

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Coco Gauff is making a big change before her start at the 2025 U.S. Open in New York. 

The American tennis star has parted ways with Matt Daly, one of her coaches, while bringing in biomechanics expert Gavin MacMillan, according to multiple reports.

"Only have good things to say about Coco, enjoyed working with her," Daly told Bounces, confirming their split. 

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Coco Gauff returns a shot in the Cincinnati Open quarterfinal match against Jasmine Paolini at the Lindner Family Tennis Center in Mason, Ohio, on Friday, Aug. 15, 2025. (IMAGN)

Why would the 21-year-old make the switch now before the final Grand Slam of the year? The answer may have to do with her serve.

Since her shocking first-round exit at Wimbledon, Gauff has struggled with her serve, which plays a tremendous factor in beating the best in the world, especially in tournaments like the U.S. Open. 

COCO GAUFF STUNNED IN STRAIGHT SETS IN FIRST ROUND OF WIMBLEDON LESS THAN A MONTH AFTER WINNING FRENCH OPEN

MacMillan has a history of fixing one of the best serves in women’s tennis, as world No. 1 Aryna Sabalenka used his expertise to correct that part of her game. 

MacMillan was spotted on the Arthur Ashe Stadium court Wednesday morning as Gauff was hitting with Elina Svitolina. 

Coco Gauff reacts in the Cincinnati Open match against Jasmine Paolini in Mason, Ohio, on Friday, Aug. 15, 2025. (IMAGN)

"A lot of things add up, and this could be a really good relationship," ESPN’s Darren Cahill told Forbes about Gauff and MacMillan. "He’s very thorough.… I’ve spoken to him many, many times before, and the fact that he’s got