MELBOURNE, Jan 30 — Ashleigh Barty’s coach believes the world number one will not win the only Grand Slam missing from her resume unless the US Open changes its balls.

Top seed Barty’s triumph at the Australian Open yesterday earned her a third Slam after the French Open in 2019 and Wimbledon last year.

But getting her hands on the trophy at Flushing Meadows to complete a career Grand Slam of all four majors is unlikely to happen with the balls currently used in the women’s singles in New York.

"The US Open really needs to change the ball for the girls. The fact they still use a different ball for guys and girls, it’s a terrible ball for someone like Ash,” Barty’s coach Craig Tyzzer said after her Melbourne Park victory over Danielle Collins.

While Wilson balls are used for both, a lighter, less fluffy version — regular duty compared to extra-duty — is deployed for the women’s competition, with the perception that they are faster.

It is the only major to use different balls for men and women.

Tyzzer said the light ball was hard to control, and Barty was forced to use a different racquet at the tournament last year.

"It was the only tournament last year, and really for two years, where she uses a gut racquet but I had to change her to a poly just to get any sort of control of the ball,” he said.

"If they keep that ball the same, no one like Ash will win that tournament.”

Barty struggled at the US Open last year, upset by unseeded American Shelby Rogers in the third round. She is yet to go beyond the fourth round in six attempts.

Last year’s US Open final was contested by shock British qualifier Emma Raducanu — the eventual winner — and Canadian Leylah Fernandez, with Tyzzer not surprised to see an all-unseeded final.

"There’s no surprise when the ball is like it is,” he said. — AFP