US Open 2025: Coco Gauff turns to Aryna Sabalenka’s former biomechanics coach on eve of Grand Slam

Tweaking technique heading into a tournament with such frenzied attention and high stakes feels like a risky move, but it might pay off for a player who is often able to recover mentally from technical malfunctions during matches.

However, hitting 16 double faults in her Cincinnati defeat by Italy’s Jasmine Paolini was a final straw, and prompted immediate action.

On Wednesday, Gauff stayed on the practice courts with MacMillan in persistent rain – showing the lengths she is going to in order to fine-tune her game before the singles starts on Sunday.

MacMillan’s anatomical study of Sabalenka focused on improving her fluidity, weight shift and angles, working intensely on her forehand as well as her serve.

It led to the Belarusian’s transformation from a top-10 player into a Grand Slam-winning champion who has dominated the WTA Tour for most of the past two years.

In an interview with Performance-Plus Tennis last year,, external MacMillan spoke about the difficulties of improving technique with limited practice time during the grind of the WTA Tour.

The Canadian, who played ice hockey as a teenager before switching to a tennis scholarship, has little time before Gauff begins her US Open campaign.

Therefore, rebuilding her confidence is likely to be as important as technique before Gauff faces Australia’s Ajla Tomljanovic – ranked 84th in the world – in the first round at Flushing Meadows in several days’ time.