"Coco Gauff's fighting demons" - Serena Williams' ex-coach Rennae Stubbs gives American 1 important advice after US Open loss to Naomi Osaka

Serena Williams' ex-coach, Rennae Stubbs, highlighted the shortcomings in Coco Gauff's game after her loss to Naomi Osaka in the fourth round of the 2025 US Open. Stubbs was also full of praise for the Japanese player who, she believes, has become more "complete."

On Monday, September 1, third seed Gauff was expected to battle it out against 23rd seed Osaka in the fourth round of the US Open. However, it was a comfortable outing for the two-time champion who registered a 6-3, 6-2 win over the home favorite.

After the match, in her podcast episode 'CYA', Stubbs, who has coached the likes of Serena Williams and Eugenie Bouchard, pointed out Gauff's issues. Initially, she mentioned where Osaka has improved and claimed it was the "opposite" for Gauff. She said (from 18:30):

"Coco’s not comfortable. She’s fighting demons. She’s fighting her serve. She’s fighting her forehand. Gavin’s come in to try and do his best to kind of correct some of the stuff, but that’s impossible to do in a week. It’s impossible."

She doubled down on claiming that it was not possible to change the World No. 3's game in a matter of weeks. Stubbs further advised Gauff and her newly appointed coach, Gavin MacMillan, to take the rest of the season off.

"I think she should take the entire rest of the year. The whole rest of the year and break every single thing down. Because today we saw a complete tennis player in Naomi Osaka. She has a more complete serve. She has a better grip on her. She sees a short ball. She knows where she’s going with it," Stubbs said.

"With the way Coco is, sometimes it’s like she doesn’t know whether to go high with the loopy or the… I mean, match point was just a basic forehand in the middle of the net. So it’s like Naomi is a more complete tennis player right now," she added.

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Serena Williams' ex-coach Rennae Stubbs noticed improvement in Coco Gauff's serve at the US Open

(L-R) Dylan Dreyer, Rafael Nadal, Cori "Coco" Gauff, Serena Williams, and Venus Williams at the 2019 Palace Invitational - Source: Getty

In the first round of the 2025 US Open, Serena Williams' ex-coach, Rennae Stubbs, noticed an improvement in Coco Gauff's serve.

"Coco doing a better job of getting the ball toss behind her head for the kick serve. Obviously trying to manage that and get better shape on it to clear the net. Hitting 11am 🕚 and not 1pm on the ball. When she tosses it too far to the right 1pm/2pm it drags her head down," Serena Williams' ex-coach, Rennae Stubbs, wrote on X

Rennae Stubbs ♈️

@rennaestubbs

Coco doing a better job of getting the ball toss behind her head for the kick serve. Obviously trying to manage that and get better shape on it to clear the net. Hitting 11am 🕚 and not 1pm on the ball. When she tosses it too far to the right 1pm/2pm it drags her head down .

The World No. 3 has brought in biomechanics expert Gavin MacMillan to help improve her service game. She has claimed multiple negative records related to her serve, including the fifth-most double faults in a WTA match and hitting the most double faults on tour in 2025.

21-year-old Gauff's record in 2025 stands at 38-13. She has won only one title this year, the French Open. She finished runner-up at the Madrid Open and the Italian Open after helping Team USA win the United Cup earlier in the year.