'It was very sudden' - why Gauff hired Sabalenka's old serve guru

Gauff cut a frustrated figure during her serving woes at the recent Cincinnati Open

American world number three Coco Gauff says it was a "sudden decision" to hire the biomechanics expert who helped rival Aryna Sabalenka overcome her serving troubles.

Gauff, 21, decided to reshuffle her coaching team on the eve of the US Open after hitting a high amount of double faults in her last three matches at the recent Cincinnati Open.

Matt Daly - a grip specialist who worked on her serve and forehand - paid the price and left his role with Gauff, despite helping her win the French Open title in June.

Instead, she has been working on the US Open practice courts this week with technique coach Gavin MacMillan, who is widely credited with improving Sabalenka and enabling her to win three Grand Slam titles.

Gauff's other coach, Jean-Christophe Faurel, remains part of the team.

"Gavin became available. I just felt this was the best decision for my game and I had to go with what I was feeling," said Gauff.

"Matt is a great coach, a great person, and I love working with him. We had a very successful partnership, but I'm just looking at long term."

It is a bold move in the lead-up to Gauff's home Grand Slam, where she landed her maiden major title two years ago.

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 exit against 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, 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 adjusting technique before Gauff faces Australia's Ajla Tomljanovic - ranked 84th in the world - in the first round at Flushing Meadows.