Coco Gauff at the 2025 US Open: A Deep Analysis

Coco Gauff entered the 2025 US Open as the reigning Roland Garros singles champion and the World No. 3. This status solidified her standing as one of the tour’s dominant forces, a position further validated by a hard-court title victory at the Wuhan WTA 1000 tournament earlier in the season. However, this period of championship success was simultaneously undermined by an acute technical liability: her increasingly unstable service game, which threatened to cap her potential. This service crisis had manifested in alarming double-fault rates in the preceding summer hard-court swing, including 23 double faults in Montreal and 16 during her loss in Cincinnati.

The US Open campaign quickly became defined by the audacious, last-minute strategic intervention implemented by Gauff’s team. Just days before the tournament commenced, Gauff overhauled her serve by parting ways with her previous coach and hiring biomechanics specialist Gavin MacMillan. This decisive action signaled a prioritization of long-term structural sustainability over the pursuit of immediate tournament success.

The campaign concluded with a fourth-round defeat (R4) to a resurgent Naomi Osaka. Nevertheless, Gauff’s short run was highly instructive, characterized by intense technical volatility in the early rounds—specifically against Ajla Tomljanovic and Donna Vekic—and remarkable demonstrations of psychological fortitude. The 2025 US Open performance should be assessed not as a defense of a major title, but as a necessary and calculated “stress test” for a foundational biomechanical modification, generating critical high-stress performance data essential for Gauff’s future dominance.

Pre-Tournament Strategy: The Biomechanical Imperative

The Acute Service Crisis Diagnosis

The abrupt change in Gauff’s support staff was necessitated by the growing, quantitative risk posed by her serve. Leading into the US Open, Gauff had accumulated 320 double faults across 48 matches, averaging nearly seven per match. This instability was not merely a loss of free points but a direct contribution to opponent success. For instance, in her Cincinnati quarterfinals loss against Jasmine Paolini, a staggering 62 of Paolini’s 85 points (72 percent) resulted directly from Gauff’s unforced errors. These metrics confirmed that the service instability represented a profound, structural issue that exceeded acceptable elite thresholds and threatened the sustainability of her top-tier performance.

Gauff confirmed that the decision to address this was driven by necessity, stating that the high double-fault rates were unsustainable and that the rapid decision to change was “the best decision for my game”.

The High-Stakes Pivot to Gavin MacMillan

To solve this technical problem, Gauff replaced her coach just days before the event, pivoting to Gavin MacMillan, a specialized biomechanics expert. MacMillan’s hiring was a significant technical commitment, shifting the focus away from conventional coaching methods toward a scientific analysis of her service motion.

MacMillan is globally renowned for solving the service crisis faced by World No. 1 Aryna Sabalenka, who transitioned from leading the WTA Tour in double faults in 2022 (428 total) to ranking 46th by 2025. MacMillan’s methodology focuses on physical foundations, emphasizing balance, spinal stability, and proprioception—the body’s awareness of its position in space—as opposed to psychological or superficial adjustments. Gauff expressed confidence in MacMillan’s history, hoping to “just take on his knowledge and see what can happen”. The implementation of these changes was immediate and intense, with Gauff reporting spending “a lot of time on court last week literally serving until my shoulder was hurting”.

The decision to compete with an unfinished service motion immediately under the intense pressure of a home Grand Slam was a calculated, high-risk strategy. By moving swiftly to implement the change, Gauff’s team demonstrated a prioritization of foundational correction over immediate competitive outcome. Competing in Arthur Ashe Stadium, the ultimate high-stress environment, effectively turned the tournament into a “live biomechanical trial.” This provided MacMillan with crucial, high-fidelity diagnostic feedback on where the new technique failed under maximum duress—data that practice sessions alone could not generate. Gauff was aware of this trade-off, acknowledging she would “not going to serve the best” during the transition phase.

Navigating the Early Rounds: Technical Volatility and Mental Fortitude

Round 1: A Three-Hour Biomechanical Resistance Test (vs. Ajla Tomljanovic)

Gauff’s first-round victory over Ajla Tomljanovic (6-4, 6-7(2), 7-5) was a three-set, two-hour and 57-minute marathon that immediately confirmed the instability of the new service motion. The match statistics reflected the difficulty of the transition: Gauff committed 10 double faults, was broken six times, and registered a 61% first-serve percentage. This instability confirmed Gauff’s difficulty in fighting “not to go back to old habits in those tighter moments”.

However, Gauff’s world-class athletic defense and ground game served as a vital competitive buffer. Her exceptional retrieval skills allowed her to dictate points and force errors, compensating for the service damage. She forced Tomljanovic into a total of 56 unforced errors while only yielding 12 winners to the Australian. This demonstrated that Gauff’s elite defensive capacity provided a necessary protective layer, enabling her to win matches despite the fragility of her first strike. This defensive superiority allowed her to remain in the tournament and continue the biomechanical experimentation, a luxury few other players could afford while making such a fundamental change.

Round 2: The Public Unraveling and High-Order Reset (vs. Donna Vekic)

The second-round match against Donna Vekic (7-6(5), 6-2) tested Gauff’s psychological resilience to its limit. The victory was marred by acute emotional distress. Gauff’s technical struggles continued in the first set, recording seven double faults and being broken at 4-4. Trailing 4-5, the pressure of the moment—exacerbated by her technical experimentation at a home major—led to a public breakdown. Gauff was “visibly shaking,” sobbing into a towel, and later described it as “the worst I’ve ever felt on the court”.

The recovery from this crisis showcased remarkable professional maturity and high-level emotional compartmentalization. When Vekic took a medical timeout late in the first set, Gauff, instead of retreating mentally, remained on court hitting practice serves, effectively turning the interruption into an open-air technical lesson. She also took a bathroom break to reset her focus. This immediate cognitive restructuring—translating emotional distress into targeted technical practice—served as a catastrophic reset button. The effect was measurable: Gauff stabilized her serve in the second set, conceding zero service breaks and hitting only a single double fault. She subsequently eased into the next round with a comfortable victory over Magdalena Frech, where her service problems had “largely abated”.

The Tactical Decisive Point: Fourth Round vs. Naomi Osaka

Gauff’s tournament concluded decisively in the Fourth Round against a resurgent Naomi Osaka, losing 6-3, 6-2 in just 64 to 65 minutes.

Osaka’s Clinical Efficiency

The defeat was directly attributable to Osaka’s peak performance, which exhibited clinical control and gave Gauff no margin for error. Osaka, playing arguably her best match in years, showcased devastating serving metrics, winning an exceptional 85% (32/38) of her service points and converting every break point opportunity she generated. She also maintained exceptional consistency from the baseline, committing only 12 unforced errors for the entire match.

This match established the operational threshold for Gauff’s new technique. While her defensive skills previously compensated for service volatility against lesser-ranked or injured opponents, Osaka’s surgical efficiency and dominant service game provided zero openings. Gauff’s usual strategy of extending rallies failed because Osaka’s serve offered no weak returns, and her groundstrokes were too precise to draw high error counts. This loss confirmed that the new, fragile service mechanics could not yet withstand elite return pressure, highlighting the precise area requiring further refinement.

The psychological component was also intense. Osaka, returning to her “favorite court in the world”, was able to summon “vintage” form under high pressure, effectively transferring the psychological weight of the encounter onto Gauff, who was already dealing with internal technical stress. Gauff later acknowledged the pressure weighed heavily, stating the level brought was “not the level that I wanted to bring”.

Comparative Analysis and Future Outlook

The strategic nature of Gauff’s 2025 US Open campaign is best understood when contextualized against her other major results.

2025 Grand Slam Metric Comparison

Gauff’s Roland Garros victory highlighted that clay courts—a surface that mitigates service speed and rewards defense—maximized her core strengths. The stark difference between her clay-court success and her hard-court struggle at the US Open highlights the technical vulnerability specifically on the hard-court surface, which demands the most reliable first strike.

Table 1: 2025 Grand Slam Singles Performance Comparison

Tournament	Result	Key Opponents Defeated	Surface	Primary Takeaway
Australian Open	4th Round (Loss to Linette)	Maria Sakkari	Hard	Solid performance but lacked title-winning depth
Roland Garros	Winner	Aryna Sabalenka, Madison Keys, Jasmine Paolini	Clay	Second Major Title; defense and consistency maximized
Wimbledon	1st Round	N/A	Grass	Early exit increased pressure for US Open
US Open	4th Round (Loss to Osaka)	Magdalena Frech, Donna Vekic, Ajla Tomljanovic	Hard	Technical transition exposed under pressure

Post-US Open Revalidation and Strategy

The US Open, despite the competitive setback, proved to be an essential diagnostic period. The high-stress data points collected in the early rounds (particularly the moments where “old habits” resurfaced) provided MacMillan with crucial, actionable information needed to refine the technique.

This interpretation is strongly supported by Gauff’s immediate, subsequent success at the Wuhan WTA 1000 tournament. Shortly after her US Open exit, Gauff secured the Wuhan hard-court title against Jessica Pegula, doing so without dropping a single set across five matches. This victory made her the first WTA player to win each of her first nine hard-court singles finals. This rapid revalidation on a hard-court surface suggests the US Open was an isolated technical anomaly related to the timing of MacMillan’s integration, rather than a permanent decline.

Gauff’s proactive decision to fundamentally overhaul a weak, but functional, aspect of her game, even at the cost of immediate US Open glory, demonstrates an exceptional level of professional maturity. This prioritization of long-term dominance—ensuring service sustainability for the remainder of her career—over short-term seasonal expectations validates the strategy taken by her team.

Conclusion and Recommendations for Service Sustainability

The 2025 US Open was a necessary crucible in Coco Gauff’s technical development. The campaign was characterized by strategic upheaval, measurable service volatility, and extraordinary psychological fortitude. The fourth-round exit confirmed the current threshold of the new technique: it requires further internalization before it can consistently withstand the aggressive return pressure applied by top-tier opponents.

MacMillan’s biomechanical changes require extended, lower-pressure repetition to shift execution from conscious effort to subconscious muscle memory. Gauff recognized this long-term commitment, expressing hope that by “this time next year, I’ll be serving much better”.

The conclusion drawn from this campaign is that the strategic gamble was fundamentally sound. Addressing the service mechanics now prevents future career plateauing. Furthermore, the immense mental resilience displayed during the second-round crisis confirms Gauff possesses the critical non-technical resources needed to endure this demanding transition period and ultimately integrate the new, reliable service motion necessary for sustained multi-surface Grand Slam dominance.