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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 between Coco Gauff and 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.
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 quarterfinal match between Coco Gauff and Jasmine Paolini at the Lindner Family Tennis Center 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 experience with different athletes from different sports, both male and female, he uses the new technology, he goes to the video a lot, really breaks down the biomechanics.”
MacMillan is the founder of Sports Science Lab, which specializes in sports performance, fitness, and physical rehabilitation.
Gauff’s game hasn’t been completely off this year, having won the French Open back in May. But her serve has been inconsistent, and she clearly wants to get ahead of that before a tournament many across the U.S. would love to see her win again on home soil.
Gauff was the 2023 champion in Flushing, Queens, but she was unable to defend her title in 2024 as she lost in the fourth round. Sabalenka went on to defeat another American, Jessica Pegula, in straight sets to claim the victory.
Coco Gauff looks on during a practice session prior to the start of the US Open at USTA Billie Jean King National Tennis Center on Aug. 20, 2025, in New York City. (Al Bello/Getty Images)
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Gauff fired her coach, Brad Gilbert, following that fourth-round exit at the U.S. Open.
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