Coco Gauff’s decision to split with longtime coach Brad Daly ahead of the U.S. Open raised eyebrows across the tennis world. But for those who have followed her game closely, the move was less about surprise and more about necessity. The 20-year-old American phenom has risen to the top tier of women’s tennis with blistering speed and athleticism, but one part of her game has persistently held her back: the serve.
That weakness came to the forefront in Cincinnati, where Gauff suffered a surprising loss to Italy’s Jasmine Paolini. Despite being the stronger player from the baseline, Gauff unraveled with a flurry of double faults, essentially handing her opponent the match. It wasn’t an isolated incident. Over the last year, Gauff has averaged nearly 12 double faults per match, and in some outings, she has piled up as many as 20. For a player ranked inside the top five in the world, that number is not sustainable.
A Specialist Hire
Instead of opting for another general coach, Gauff made the bold choice to bring in Gavin MacMillan, a biomechanics specialist whose expertise lies in understanding how the body moves during athletic performance. Tennis biomechanics focuses on joint angles, muscle activation, balance, and the efficient transfer of energy through the body’s kinetic chain. In practical terms, that means MacMillan’s role will be to overhaul the mechanics of Gauff’s serve—an issue that has haunted her career since her teenage breakthrough.
If the partnership works, MacMillan can help Gauff minimize double faults, increase consistency, and turn her serve from a liability into a weapon. In today’s game, where the serve often dictates momentum, such an upgrade could be career-defining.
Daly’s Contributions
The split with Daly was not the result of poor chemistry or failure. On the contrary, Daly helped Gauff refine her forehand—a shot once labeled shaky by analysts—and improved her grip, giving her more stability in long rallies. Under his guidance, she also showed significant growth in court positioning and tactical discipline.
But coaching in tennis is often about timing. Gauff reached a point where incremental improvements in her groundstrokes were not enough to push her past the very top echelon of the WTA Tour. Her serve remained the glaring weakness, and a technical overhaul required the kind of specialist expertise Daly could not provide.
Learning from History
Gauff’s move is not unprecedented. Other tennis stars have made similar shifts, seeking out biomechanical or technical specialists when a chronic flaw became too costly. Maria Sharapova worked with biomechanics experts after shoulder surgery to rebuild her serve. Novak Djokovic famously tweaked his service motion mid-career to protect against injury and increase efficiency, a change that prolonged his dominance.
For Gauff, who already boasts elite speed, anticipation, and competitiveness, the serve may be the final missing piece. If corrected, it could transform her into a consistent Grand Slam threat.
High Stakes, High Reward
The risks are obvious: changing a service motion before a major tournament can lead to short-term struggles as adjustments set in. But Gauff has shown resilience before. She broke onto the scene at just 15 years old by defeating Venus Williams at Wimbledon, and since then, she has weathered enormous expectations with maturity beyond her years.
Now, she faces perhaps the most important technical challenge of her young career. If MacMillan’s work pays off, Gauff could eliminate the double-fault demons and turn her serve into a reliable platform for the rest of her explosive game.
Onward and Upward
Ultimately, the decision to replace Daly with a biomechanics coach reflects Gauff’s long-term vision. She is not content to remain a top-10 player—she wants to dominate. And for that, every weakness must be addressed with precision.
Daly’s work gave her stability; MacMillan’s task is to unlock efficiency. If successful, this coaching change may be remembered not as a gamble, but as the turning point that propelled Coco Gauff from rising star to enduring champion.
Onward and upward, indeed.
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