Just days before the 2025 US Open, Coco Gauff welcomed a new coach, Gavin MacMillan, to her team. Her primary goal was clear — to eliminate her double faults. In 2025 alone, she recorded around 306 double faults in 46 matches. That’s a worrying number, as double faults directly hand points to opponents, shift momentum, and pile pressure on Gauff. However, according to her new coach, there’s another area of her game that needs attention first.

MacMillan is the same coach who helped Aryna Sabalenka overcome her serving struggles — using biomechanics as the key to success. Now, as Gauff and MacMillan begin their partnership, many in the tennis community are wondering whether there’s more than just double faults to fix. That very question came up during MacMillan’s appearance on Tennis Channe

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