Ashleigh Barty’s coach Craig Tyzzer has given a surprise explanation for Emma Raducanu’s success at the US Open.

Raducanu stunned the world of tennis when she became the first qualifier, male or female, to win a Grand Slam.

The 19-year-old stormed to victory at the US Open in September, defeating Leylah Fernandez in the final at Flushing Meadows.

She became the first female British tennis player to win a major since Virginia Wade in 1977, and is now the world number 13. 

Unlike the rest of the sporting world, Tyzzer revealed he was not surprised that two unseeded players made it to the US Open final. He claimed the balls used at the Grand Slam made unexpected results more likely.

"You see the result at the US Open, it was two players who, you go, 'Wow, that was, two different players won that?' There's no surprise when the ball is like it is," he said.

The US Open is the only Grand Slam to use different balls for the men and women’s tournaments.

Emma Raducanu's success at the US Open has been attributed to the lighter balls at the tournament

The rule was introduced in the early 1980s after female tennis players complained the extra-duty balls were causing discomfort in their arms, shoulders and elbows.

To this day, despite advances in racket technology, the women’s tournament at Flushing Meadows still uses regular-duty Wilson balls with smoother felt to reduce friction.

Tyzzer claimed Barty "won’t win the US Open" if the balls at the Grand Slam were not changed.

The 25-year-old star, who allegedly finds the lighter balls difficult to control, has now won the French Open, Wimbledon and Australian Open, but has never made it past the fourth round of the US Open.

Ashleigh Barty is currently celebrating winning the Australian Open

"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," Tyzzer said.

"Even in Cincinnati, when they use the US Open ball outside, she could actually get some loft out of the court.

"But the ball itself is so light. It was the only tournament last year and really for two years where she uses gut racquet [strings] but I had to change her to a poly just to get any sort of control of the ball.

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

Barty is currently celebrating her victory at the Australian Open this weekend. She defeated Danielle Collins 6-3, 7-6 in front of a home crowd to win the third Grand Slam title of her career.