World number three Coco Gauff faces heightened expectations at the 2025 US Open, especially due to a significant coaching change made just days before the tournament begins in New York. Gauff replaced her longtime coach Matt Daly with biomechanics specialist Gavin MacMillan to help improve her notoriously inconsistent serve.
Former ATP world number one Andy Roddick described this last-minute move as a bold and “ambitious” decision, given the short time remaining before Gauff’s first match. He acknowledged MacMillan’s proven track record, having helped Aryna Sabalenka address similar serving struggles in 2022, but emphasized the challenges of implementing such changes so close to a Grand Slam.
“She [Gauff] has shaken up the coaching staff this week. Matt Daly out, biomechanist in, who worked with Aryna Sabalenka,”
Roddick explained on his ‘Served’ podcast.
“We forget Sabalenka had the serving yips a few years ago. We forget about that. I do think changing to biomechanics the week before you play a major seems like an ambitious thing to do.”
Roddick noted the difficulty of quickly fixing serving issues that can lead to inconsistency, especially when the problem includes mental hurdles like the “yips.” He shared a personal observation from when he worked with Gauff about a year and a half ago, highlighting that small biomechanical corrections can have significant results, but require time to integrate fully.
“This MacMillan, the biomechanic who has come in. 10 out of 10 job with Aryna Sabalenka. There is precedent for this guy being really, really good. But that was done over an off season, that was not done on a Tuesday and a Wednesday before a major, just so we are clear.”
Roddick also emphasized how difficult it is to manage double faults under pressure, though talented players like Gauff can still win big despite such struggles.
“There is no way around 20 something double faults in a match. Also, imagine being so good you could do that and win a major. It is unbelievable.”
Context of Gauff’s Serve Troubles and Coaching History
Coco Gauff’s serve has been a persistent obstacle throughout her career. In 2025, her second-serve percentage ranks lowest among the WTA’s top 25 players at 42.7%, alongside a tour-leading 320 double faults this season. This has frequently undermined her match performance despite her high-level talent and athleticism.
After working with Matt Daly for less than a year, Gauff decided to make a change by engaging Gavin MacMillan, a biomechanist, with the aim of correcting the technical flaws in her serve. MacMillan’s success with Aryna Sabalenka in overcoming similar serving difficulties provided a precedent that Gauff hopes to replicate.
The timing of this switch in coaching style, coming just before a Grand Slam at her home tournament, underscores both the urgency and the risk involved. Gauff appears confident that MacMillan’s expertise can help her refine her serve mechanics and improve consistency during critical moments.
Upcoming US Open Debut Against Ajla Tomljanovic
Coco Gauff’s first match at the 2025 US Open will be against Ajla Tomljanovic, a player known for a memorable victory over Serena Williams at Flushing Meadows in 2022. The American star will aim to defend her US Open title from 2023 with this new coaching team in place.
The two athletes have met only once before, at the 2024 Paris Olympics. Gauff opened that Olympic tournament with a commanding 6-3, 6-0 win over the Australian. She had also served as the American flag bearer alongside LeBron James during the opening ceremony, marking a moment of high national pride.
Despite the strong start, Gauff’s Olympic run ended the next round with a loss to Croatia’s Donna Vekic, who ultimately earned the silver medal. This experience demonstrated both Gauff’s potential and some of the challenges she still faces in major international competitions.
Implications of the Coaching Change for Gauff’s US Open Campaign
The late coaching adjustment reflects Gauff’s determination to address one of her most persistent weaknesses heading into a Grand Slam on home soil. While the shift to Gavin MacMillan’s biomechanical approach is promising, Andy Roddick’s insight raises caution about the limited preparation time available.
If successful, this partnership could lead to significant improvements in Gauff’s serve stability, potentially enhancing her chances of deepening her run at the US Open. However, mastering technical changes under the pressure of a major tournament will demand focus and adaptability.
Fans and analysts alike will watch closely to see how this coaching decision influences Gauff’s performance, providing insight into how last-minute strategic decisions affect elite players in high-stakes tennis environments.