Queens, N.Y.: Coco Gauff holding her trophy after defeating Aryna Sabalenka to win her first grand slam in the the Women’s Singles US Open Tennis Championships at Arthur Ashe Stadium at the USTA Billie Jean King National Tennis Center in Flushing Meadow, Queens, New York on Sept. 9, 2023 (Photo by J. Conrad Williams Jr./Newsday RM via Getty Images)

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Coco Gauff, the 2023 U.S. Open champion and 2025 Roland Garros winner, has shaken up her coaching team ahead of the U.S. Open.

Gauff has parted ways with coach Matt Daly and brought in biomechanics expert Gavin MacMillan, per ESPN. MacMillan, who received a tennis scholarship from San Jose State University and also founded a Sport Science Lab in 2001, previously worked with current world No. 1 Aryna Sabalenka to fix her troubled serve. MacMillan was shown on court with Gauff as she practiced Wednesday in Arthur Ashe Stadium, as was JC Faurel, who has been working with Gauff.

“A lot of things add up and this could be a really good relationship,” ESPN’s Darren Cahill said on air of MacMillan. “He’s very thorough ….I’ve spoken to him many, many times before and the fact that he’s got experience with different athletes from different sports, both male and female, he uses the new technology, he goes to the video a lot, really breaks down the biomechanics.”

Chris Eubanks, an ATP player and announcer, was also seen on court huddling with Gauff’s father, Corey.

“He’s always got her best interests at heart, so he’s a great friend of Coco’s,” Cahill said.

Gauff parted ways with Brad Gilbert last year after Gauff’s fourth-round exit at the U.S. Open, where she failed to defend her title.

Gauff is 4-4 since winning Roland Garros and lost to Jasmine Paolini in the quarterfinals in Cincinnati.

“It’s crazy how quickly you can lose your confidence,” ESPN’s Mary Joe Fernandez said this week on air. “You win a Grand Slam title and you think you’re riding this wave and it’s going to carry over and it doesn’t always happen. For Coco, she had a really tough draw at Wimbledon, playing [Dayana]

Yastremska in the first round, a big powerful hitter, so that was I think unfortunate for her not being able to work her way into the tournament.

“And then on the hardcourts she has struggled, primarily with her serve. I think that’s the one shot that if she can settle down and find a way to feel confident that she’s going to make a majority of her first serves and rely on what she did a couple years ago, winning when she wasn’t playing her best and making her opponents beat her some how, making it more physical, then I think she’ll get back to it. But right now, for me, it’s mental.”

Gauff did not participate in the Mixed Doubles event at the U.S. Open this week, preferring not to “waste mental energy” on it, so she could focus on singles.

The singles draws begin Sunday.