Looking to win her second Grand Slam title of the year in New York, Gauff has made a big move before the US Open.
Earlier this year, Gauff defeated Aryna Sabalenka in Paris to win the second Grand Slam title of her career.
Unfortunately for the American, her form has dipped since, losing her opening matches at the Berlin Open and Wimbledon on grass.
Continuing to struggle, Gauff fell in the fourth round of the Canadian Open and the quarterfinals of the Cincinnati Open.
In a bid to turn things around, Gauff replaced coach Matt Daly with Gavin MacMillan just days before the start of the US Open.
Reacting to the news, Serena Williams’ former coach was very impressed with the hire.
Rick Macci thinks hiring Gavin MacMillan was ‘the best decision’ of Corey Gauff’s life
Williams’ former coach, Rick Macci, believes Corey Gauff (Gauff’s father) made the right call in bringing MacMillan into the team.
“Corey Gauff just made the best decision in his life for Coco [Gauff],” said Macci.
“By hiring Gavin MacMillan, this can be solved real quick and make her serve click.
“What she hears will be 100% different from anything in the past.
“He knows the issue and understands joint angles and soft tissue.
“Career changer!”
MacMillan, a biomechanics expert, was seen helping Gauff with her serve in a practice session on Arthur Ashe Stadium ahead of the US Open.
The serve has been a problem area for Gauff recently, struggling with the shot since winning the French Open in June.
Macci believes MacMillan will sort her serve out, as he recalled the success the Canadian achieved alongside Aryna Sabalenka.
“This is not only a game changer for Coco hiring Gavin MacMillan, but a major league career changer,” he said.
“I saw the modifications biomechanically he did with [Aryna] Sabalenka on her serve, and he rewired everything from start to finish.
“A biomechanical expert knows exactly the real culprit, not a symptom others say and see.
“Game, set, and match. Gauff!”
Macci is confident that Gauff will improve with MacMillan alongside her, but just how poor has the serve been recently?
Coco Gauff’s double-fault count since winning the French Open
Since winning the French Open three months ago, Gauff has made five or more double faults in all but one of the eight matches she’s played.
| Match | Opponent | Result | Score | Double faults |
| Berlin Open – 2R | Wang Xinyu | Loss | 3-6, 3-6 | 7 |
| Wimbledon – 1R | Dayana Yastremska | Loss | 6-7, 1-6 | 9 |
| Canadian Open – 2R | Danielle Collins | Win | 7-5, 4-6, 7-6 | 23 |
| Canadian Open – 3R | Veronika Kudermetova | Win | 4-6, 7-5, 6-2 | 14 |
| Canadian Open – 4R | Victoria Mboko | Loss | 1-6, 4-6 | 5 |
| Cincinnati Open – 2R | Wang Xinyu | Win | 6-3, 6-2 | 8 |
| Cincinnati Open – 4R | Lucia Bronzetti | Win | 6-2, 6-4 | 3 |
| Cincinnati Open – QF | Jasmine Paolini | Loss | 6-2, 4-6, 3-6 | 16 |
Her worst serving performance came in the second round of the Canadian Open, where she made 23 double faults against Danielle Collins.
Giving up almost a set’s-worth of points in double faults, Gauff was lucky to escape with the win in three sets.
Having struggled as much as she has, Gauff deserves real credit for making the bold move to hire a coach with experience in fixing serves.
During his time with Sabalenka, MacMillan transformed the Belarusian’s serve from a weakness to a real strength.
Aryna Sabalenka’s serve compared to the WTA Tour – 2022
- Aces – 6th (249)
- Double faults – 1st (428)
- 1st Serve % – 207th (59.7%)
- 1st Serve points won % – 39th (67.7%)
- 2nd Serve % – 210th (41.8%)
- Serve points won % – 85th (57.3%)
- Service games won % – 80th (67.7%)
Aryna Sabalenka’s serve compared to the WTA Tour – 2025
- Aces – 6th (217)
- Double faults – 42nd (217)
- 1st Serve % – 132nd (62.4%)
- 1st Serve points won % – 25th (68%)
- 2nd Serve % – 20th (50.5%)
- Serve points won % – 7th (61.4%)
- Service games won % – 9th (76.6%)
Making the changes, Sabalenka was transformed from a perennial Grand Slam contender to a three-time major champion and world number one.
If MacMillan can help Gauff find the same improvements, then perhaps she, too, could ascend to the top of the world rankings.
Currently ranked third in the world, with two Grand Slam titles to her name, Gauff has been a step behind Sabalenka (#1) and Iga Swiatek (#2) over the last few years.
Gauff will no doubt hope MacMillan is the right coach to help her take the next step and challenge for the number one ranking.
Only time will tell whether or not their partnership will be successful, but it will certainly be interesting to see how she performs during their first tournament together.
Gauff and MacMillan are set to begin their coaching relationship at the US Open, which starts on Sunday, August 24.
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