Aryna Sabalenka reacts to Coco Gauff hiring her old coach ahead of the US Open

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Coco Gauff made a bold move right before the US Open that shocked many tennis fans.

Despite winning the French Open with Matt Daly in June, the world number three decided to make a coaching move on the eve of the final Grand Slam of the year.

Gauff has replaced Daly with Gavin MacMillan, a biomechanics expert, who previously helped Aryna Sabalenka fix her serve.

The American star is in need of some help with her serve, as her double-fault count has risen over the last few months on the WTA Tour.

During her pre-tournament press conference, Sabalenka gave her verdict on Gauff and MacMillan’s new coaching relationship.

Aryna Sabalenka wishes Coco Gauff and Gavin MacMillan the ‘very best’

Asked for her thoughts on MacMillan, Sabalenka was full of praise for the Canadian, as she wished him and Gauff the best.

“Yeah, I’m really grateful for his help during really tough times. For me, he really helped me with the serve. I really appreciate him for everything,” she said.

“You know, everyone is different. I was really desperate for changes, and I was ready to change whatever, to change my serve and to get better and to finally, you know, get back on track with my serve. So for me, it was basically, like, a couple of weeks, and I was sort of fixed.

“But everyone is different, and I wish them both the very best, and hopefully everything can work out well for them.”

Reflecting on her time working with MacMillan, Sabalenka didn’t remember it taking much time at all before the results of their work began to show.

“You know, for me wasn’t really hard, because I tried literally everything, and nothing would help me to fix my serve. It was the last step before I would say, Okay, bye-bye, tennis,” she said.

“I was so desperate, so I wasn’t really doubting my decision.

“The moment we started working, I felt like, Okay, there is something. I definitely have a better feeling on my serve.

“I just trusted the process, trusted myself. Like the first tournament I played, I already felt the difference, and I felt, Okay, I’m getting there.

“So for me it was just about repetitions, a little bit of time, and, like, full commitment to whatever he was saying.”

Looking back at Sabalenka’s serving numbers in 2022, it’s clear to see the positive effect MacMillan had on her game.

Sabalenka’s double fault count reduced dramatically within a few weeks, propelling her to back-to-back semifinal appearances at the Cincinnati Open and US Open.

Gauff will be hoping MacMillan can have the same effect on her game, as she searches for her second US Open title.

How many double faults has Coco Gauff been making recently?

Whilst her double fault numbers aren’t quite as bad as Sabalenka’s were in 2022, they’ve been trending in the wrong direction for Gauff over the past few months.

Since Wimbledon, Gauff has made fewer than five double faults in just one of her six matches, a worrying tally for someone with her talent.

• 2025 Canadian Open 2R v Danielle Collins [WIN] – 23 double faults
• 2025 Canadian Open 3R v Veronika Kudermetova [WIN] – 14 double faults
• 2025 Canadian Open 4R v Victoria Mboko [LOSS] – 5 double faults
• 2025 Cincinnati Open 2R v Wang Xinyu [WIN] – 8 double faults
• 2025 Cincinnati Open 4R v Lucia Bronzetti [WIN] – 3 double faults
• 2025 Cincinnati Open QF v Jasmine Paolini [LOSS] – 16 double faults

Those numbers simply aren’t good enough to win big events on tour, which is likely the reason why Gauff decided to bring in MacMillan.

If she can develop her serve into a weapon, just as Sabalenka has done, then there truly would be no limit to what Gauff can achieve on the WTA Tour.

Gauff will begin her coaching relationship with MacMillan at the US Open, where she will play her first-round match against Australia’s Ajla Tomljanovic.