Who is Coco Gauff's new team member Gavin MacMillan? Meet the biomechanics expert who led Aryna Sabalenka to greatness after serve struggles

Coco Gauff sent shockwaves across the tennis world earlier on Wednesday (August 20) with a rather important decision ahead of her US Open campaign. The World No. 3 has roped in biomechanics expert Gavin MacMillan, who previously worked with Aryna Sabalenka, into her team to work on her serve, which has gone through its share of woes recently.

Gauff has replaced long-term coach Matt Daly with Sport Science Lab CEO MacMillan if incoming reports from ESPN are anything to go by. Although Daly was successful in his tenure with the 21-year-old, guiding her to titles in Paris, Riyadh, and Beijing, he, along with fellow team member J.C. Faurel, is now out the door as the final Major tournament of the year looms ahead of the former titlist.

For those unaware, Aryna Sabalenka first courted Gavin MacMillan's services in early 2022. The then-23-year-old had a serious tendency to commit a slew of double faults back then, and by her own admission, they were completely done away with under the Sport Science Lab founder's supervision.

"I'm really glad that happened to my serve," Aryna Sabalenka told Tennis Channel last year. "I was forced to hire someone like Gavin. I was forced to learn something new.”

Sabalenka also reaped the benefits of MacMillan's insights on her forehand wing, allowing her to take more controlled swipes at the ball.

"Before I was trying to over-rush things, try to run to the ball, meet it earlier," she added in her account to Tennis Channel in 2024. "But in my case, I have to actually wait for the shot and wait for the right moment to actually hit the forehand, to make that rotation, which gives me much more power and control on the shot."

The Belarusian's serve prowess has certainly gone up in the last few years following her partnership with MacMillan. In the last 52 weeks, the 27-year-old has fired down 217 aces while only committing 122 double faults — the least in the top 5 leaderboard. For academic purposes, Coco Gauff has double-faulted 320 times across 47 matches during this period, pointing to alarming signs for her first serve.

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Coco Gauff hit 16 doube faults during her Cincinnati QF loss to Jasmine Paolini

Coco Gauff prepares to serve at Cincinnati Open 2025 | Image Source: Getty

Coco Gauff has been up and down with her service game in the last few weeks. Despite winning her second Major title at the French Open in May, the American has been unable to monopolize the WTA Tour since then as she has gone 4-4 in her last eight completed matches.

More concerningly, the consistency issues surrounding the World No. 3's second serve have undermined her recent performances. The 10-time WTA singles titlist hit 16 double faults in a 2-6, 6-4, 6-3 defeat to Jasmine Paolini in the quarterfinals of the Cincinnati Open last Friday (August 15), which came a week after a 23 double-fault display during her three-set victory against Danielle Collins in the second round of the National Bank Open in Montreal.