Coco Gauff didn’t wait for the results to come in. Less than a year after announcing her partnership with Matt Daly, a footwork and grip technique specialist, she confirmed their split.
Days before her first serve at the 2025 US Open, the American made a major coaching change, replacing Daly with a biomechanics coach known for his critical involvement with Aryna Sabalenka. Here’s who she brought in and why.
Who is Coco Gauff’s New Biomechanics Coach?
Gauff shocked the tennis world when she confirmed she split with coach Matt Daly and hired biomechanics expert Gavin MacMillan just six days before the start of the US Open.
Coco Gauff listens to freshly-hired biomechanics expert Gavin MacMillan in New York. pic.twitter.com/QOVBE2CAzm
— Jimmie48 Photography (@JJlovesTennis) August 22, 2025
The move wasn’t teased, expected, or leaked anywhere on social media or news outlets. It came as Gauff, one of the tournament favorites, admitted her serve was unraveling. She now relies on a new voice to get it under control mid-tournament.
“Yeah, it was a very like sudden decision,” Gauff told reporters. “Gavin became available, and I just felt, you know, this is the best decision for my game at least, and had to go with what I was feeling.”
MacMillan, known for his biomechanics-based serve corrections, previously worked with Aryna Sabalenka to fix her infamous 2022 serving issues. He’s now being brought in specifically to help Gauff address her own struggles from the service line.
Why did Coco Gauff Opt for the Change?
Gauff’s serve has been under scrutiny all season. She leads the WTA Tour in 2025 with over 320 double faults, committing 23 in her match against Danielle Collins in Montreal, and logging 16 in a quarterfinal loss in Cincinnati.
Daly had guided Gauff to the 2024 WTA Finals, and a title run at Roland Garros earlier in the year, but technical inconsistencies with her motion persisted.
“I know Gavin has had experience with this before,” Gauff said. “So I’m hoping I can take on his knowledge and see what can happen.”
She emphasized that Daly was “a great coach and a great person” and said the decision was long-term focused.
What Is MacMillan’s Role in Gauff’s Team?
MacMillan is not taking over full-time coaching duties. Jean-Christophe Faurel, Gauff’s long-standing mentor, is responsible for overall strategy and tournament prep. MacMillan’s role is technical and centered on rebuilding her serve.
Gauff explained the urgency behind the change.
“I felt like this is a good opportunity because I don’t have that many points to defend, honestly, in this part of the season,” she said. “I’m one of those people, I’m looking at long-term, and I’m hoping I can get it all together by… Monday or Tuesday. If not, I have the rest of this year to work on it.”
Serve sessions don’t stop for the rain! Coco Gauff and Gavin MacMillan showing their dedication + determination today. Last one’s off the practice court as rain falls at the US Open. pic.twitter.com/bvZlDPcem7
— Brenner Morton (@simonsaystennis) August 20, 2025
Gauff opened her 2025 campaign with a tight three-set win over Ajla Tomljanović. She hit 10 double faults but said she was committed to trusting the process.
“I don’t want to waste time on continuing doing the wrong things,” she said. “A tournament is a tournament. I hate losing regardless of where I am. If this was a 250, I would feel just as crazy to do it.”
Naomi Osaka beat Coco Gauff 6-3 6-0 at the 2019 US Open, back when Coco was 15 and making her Ashe debut.
Coco was left in tears, and Naomi told her she did amazing, offering her to do the on-court interview alongside her.
Six years on, they meet again ❤️pic.twitter.com/UzaOXpcHFp
— Bastien Fachan (@BastienFachan) August 30, 2025
The 2023 US Open champion remains one of the tournament favorites. She reached the fourth round with wins against Tomljanovic, Donna Vekic, and Magdalena Fręch. Her next match is scheduled for Monday against Naomi Osaka at Arthur Ashe Stadium.
