Coco Gauff stepped onto the courts of the 2025 US Open not just as a defending Grand Slam champion, but also as a player navigating change. With a fresh face in her coaching corner, the American is clearly turning a page, though her serve—long considered her Achilles’ heel—still haunts her game.
Only a year into her collaboration with Matt Daly, Gauff made headlines by ending their partnership on the eve of the season’s final major. The decision raised eyebrows, but few could argue with her choice of replacement. Gavin MacMillan, a biomechanical expert, has now been drafted in with a very specific mission: to untangle the technical knots in Gauff’s serve.
That task is not small. Prior to Flushing Meadows, the 21-year-old had racked up a staggering 320 double faults in just 47 matches, averaging nearly seven per contest. The numbers underline the urgency of the problem, and the first round in New York proved that the work ahead is steep. Against Ajla Tomljanovic, Gauff committed 10 double faults—one of them painfully coming on match point—before grinding out a 6-4, 6-7 (2-7), 7-5 victory after nearly two hours of stop-start drama.
Her performance was a mixed bag. Alongside those serving struggles, she also sprayed 59 unforced errors across the court, countered only by 29 clean winners. Reflecting on the match, Gauff admitted: “Yeah, it was a tough match. I had chances for it to be straight sets. Ajla was tough. It wasn’t the best, but I’m happy to get through to the next round.”
The reigning French Open champion acknowledged that patience was key. “I had so many chances and [I knew] eventually it was going to come. I had chances to close out in two, I had chances to go up a double break so many times, so yeah I was just like ‘eventually one of these are going to go my way and it ended up happening.”
For Gauff, the real adjustment isn’t just on the scoreboard—it’s also in her mindset following the coaching shift. “It has honestly been really tough, kinda mentally exhausting, but I am trying. It wasn’t the best today, but at 30 all it came of all came in. But it’s an improvement from last week in Cincy.”
ESPN’s broadcast team captured the moment with a sharp summary: “Far from perfect…but progress.” And that seems to be the theme for Gauff’s current campaign—incremental steps rather than instant solutions.
Already, signs of MacMillan’s input were visible. Her serve, often erratic in the past, showed subtle tweaks in motion and mechanics. The speed dipped noticeably during the opening set as she tested the new technique, before rising again in the second and third. Against Tomljanovic—herself a seasoned competitor and former US Open quarter-finalist—those adjustments were put under serious pressure, but Gauff managed to find just enough resilience to scrape through.
Before the tournament began, she was clear-eyed about why she made the change. “I needed to make a change, technical change to it, and I don’t want to waste time continuing doing the wrong things.” It is a process, one that inevitably brings frustration alongside growth, but one that could ultimately define her future trajectory.
Now, her immediate challenge is another stern test in the form of Donna Vekic, who also battled through a grueling three-setter against Jessica Bouzas Maneiro. As Gauff continues her campaign, she and MacMillan will be hoping that each match brings not only wins, but visible progress toward a more reliable, weaponized serve.