Coco Gauff Revamps Her Serve and Scrapes Through: U.S. Open

The atmosphere on Arthur Ashe Stadium was electric as Coco Gauff stepped onto the court for her first-round U.S. Open match against Ajla Tomljanović. The American tennis star, known for her powerful athleticism and fighting spirit, was about to face one of the most challenging tests of her career—not just against her opponent, but against her own serve. Despite struggling with 10 double faults and being broken six times, Gauff managed to secure a hard-fought victory: 6-4, 6-7 (2), 7-5 in nearly three hours of intense play. This match wasn’t just about advancing to the next round; it was the first public test of a bold technical overhaul of her serve, guided by biomechanics expert Gavin MacMillan. This post delves into Gauff’s journey to reinvent her most problematic shot while competing on tennis’s biggest stage.

The Serve Struggle: A Long-Standing Challenge

🎾 The Double Fault Dilemma

For years, Coco Gauff’s serve has been a paradox—a weapon capable of unleashing rockets at nearly 130 mph, but also a liability that has cost her critical points and matches. In 2025 alone, she accumulated 320 double faults, the highest on the WTA Tour and nearly 100 more than the next player on the list. This inconsistency reached a breaking point in matches like her loss to Emma Navarro at Wimbledon and a grueling win over Danielle Collins in Montreal, where she served 23 double faults in a single match.

🔧 Previous Attempts at Fixes

Gauff and her previous coach, Matt Daly, had tried minor tweaks, including adjusting her grip. However, these changes only provided temporary relief without addressing the fundamental biomechanical flaws in her service motion. The serve’s inherent inefficiencies made it unreliable under pressure, leading to bouts of double faults that undermined her confidence and results.

The Gavin MacMillan Factor: A Sudden but Strategic Change

🤝 A Last-Minute Decision

Just days before the U.S. Open, Gauff made a sudden coaching change, bringing in Gavin MacMillan, a biomechanics specialist renowned for solving Aryna Sabalenka’s serve issues. MacMillan’s approach is rooted in science, not psychology. He believes double faults occur not because of stress but because of a flawed service motion that fails under pressure.

🔬 The Science Behind the Changes

MacMillan’s methodology focuses on:

• Proper toss alignment: Ensuring the tossing hand’s palm faces the sky to promote better shoulder alignment.
• Spinal engine theory: Using the spine as the primary driver of power and movement.
• Consistent joint angles: Creating optimal 90-degree angles for maximum efficiency and repeatability.

For Gauff, this meant rebuilding her serve from the ground up—a process she described as “mentally exhausting” and akin to “learning a new language”.

The US Open Test: Balancing Old Habits and New Techniques

📊 Serve Performance Against Tomljanović

In her first-round match, Gauff consciously prioritized form over power. Her first-serve speeds started cautiously at 88 mph in the first set, gradually increasing to 101 mph by the third set as she gained confidence. Despite hitting 10 double faults, she also produced moments of brilliance, including a crucial second-serve ace at 88 mph.

💪 Mental Resilience and Adaptability

Gauff’s victory was a testament to her mental toughness. After failing to close out the match at 5-4 in the third set—succumbing to old habits with consecutive double faults—she broke back immediately and sealed the win on her second attempt. As she later reflected, “I had so many chances… I was just like, ‘Eventually, one of these is going to go my way’”.

Technical Breakdown: What’s Changing in Gauff’s Serve?

⚙️ Key Adjustments

1. Toss Consistency: MacMillan emphasized eliminating the toss’s drift to the right, which caused Gauff’s body to collapse and the ball to land in the net.
2. Reduced Serve Speeds: Initially, Gauff focused on slower but more accurate serves to build rhythm and avoid double faults.
3. Height of Contact: Addressing her low contact point to improve power and consistency.

📈 Comparative Serve Data

Table: Coco Gauff’s Serve Speeds and Double Faults in Recent Matches

The Bigger Picture: Why This Change Matters

🏆 Long-Term Career Implications

Gauff’s decision to overhaul her serve mid-season reflects her ambition and maturity. Rather than resting on her achievements—including two Grand Slam titles and a career-high ranking of No. 2—she is focused on addressing weaknesses to dominate the sport for years to come. As she stated, “I’m not going to waste time playing the way I don’t want to play”.

🌍 Comparison to Other Elite Adjustments

Gauff joins players like Jannik Sinner and Iga Świątek, who made foundational technical changes to evolve their games. Similarly, Aryna Sabalenka’s collaboration with MacMillan transformed her from a double-fault-prone player into the world No.1.

Conclusion: The Journey Ahead for Coco Gauff

Coco Gauff’s first-round victory at the U.S. Open was more than a win—it was a statement of intent. By embracing a biomechanical overhaul of her serve, she has embarked on a path that could define the next phase of her career. While the process is challenging and far from complete, her resilience and willingness to evolve demonstrate the mindset of a champion. As the tournament progresses, all eyes will be on how her new serve holds up under pressure—and whether this change will propel her to the top of the rankings.

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