As Coco Gauff stepped onto the court for her opening match at the 2025 U.S. Open, the focus wasn’t just on her opponent, Ajla Tomljanović, but on a fundamental and risky change to her game. Despite a triumphant season that includes winning the French Open, the 21-year-old American has embarked on a “hard reset” of her most potent yet perilous weapon: her serve.
The decision comes after a period of frustrating inconsistency. While Gauff’s serve can be a blistering, near-130 mph asset, it has also been a significant liability. According to The Athletic, she has hit 311 double faults in 2025, the most on the WTA Tour and a staggering 96 more than the next player. Recent matches highlighted the urgency of the issue; she recorded 23 double faults in a single match in Montreal and 16 in a quarterfinal loss in Cincinnati. This feast-or-famine delivery has been a recurring theme throughout her career, often forcing her to rely on her exceptional athleticism and fighting spirit to win matches.
Recognizing that minor tweaks were no longer sufficient, Gauff’s team made a decisive move just before the start of the U.S. Open. They enlisted the help of Gavin MacMillan, a renowned biomechanics expert credited with transforming Aryna Sabalenka’s service game. Sabalenka, once plagued by double faults, went on to become a U.S. Open champion and World No. 1 after working with MacMillan. Gauff has replaced Matt Daly, a grip expert who had been part of her team, with MacMillan in a bid for long-term sustainability. “I needed to make a change, technical change to it, and I don’t want to waste time continuing doing the wrong things,” Gauff stated in a pre-tournament press conference.
The effects of this reconstructive surgery on her service motion were immediately apparent in her first-round match. As reported by live coverage from The Athletic, Gauff had an “inauspicious start,” delivering a double fault and being broken in her opening service game. Her serve speeds were noticeably lower, hovering around 77 to 85 mph as she focused on ingraining the new technique. However, showcasing her trademark resilience, Gauff battled back, breaking Tomljanović’s serve to level the set and eventually take control.
This bold move comes at a time when Gauff has already solidified her place at the pinnacle of the sport. With two Grand Slam singles titles—the 2023 U.S. Open and the 2025 French Open—and a total of 10 career singles titles, she has achieved a career-high ranking of World No. 2. Her success also extends to doubles, where she won the 2024 French Open with partner Kateřina Siniaková. Yet, her willingness to undertake such a significant technical overhaul on the eve of defending her home Slam underscores a deep commitment to continuous improvement.
While the timing may seem perilous, Gauff views it as a necessary investment in her future. She is not content to win matches in spite of her serve; she aims for a level of dominance that a reliable, powerful serve can provide. “I’m looking at long term,” Gauff said. “I have a clear future where I see myself, and I feel like I’m really close. I think this aspect of the game will bring everything together for me.” The 2025 U.S. Open may be the first public test of this new motion, but for Gauff, it’s a crucial step toward realizing her full potential.
