The issue came to a head 16 months ago at the US Open final when Serena Williams was penalised for receiving hand signals from her coach Patrick Mouratoglou during her loss to Naomi Osaka.

Acknowledging the rules were difficult to enforce, the WTA will now allow words of encouragement and hand signals from coaches in the players box.

The trial will begin next month and apply to all Premier and International tournaments in 2020.

Late last year, Cahill rejoined two-time major winner Simona Halep's team, with the Romanian advancing to the Australian Open quarter-finals on Monday with a straight-sets win over Belgian Elise Mertens.

"I'm for it," Cahill said of the WTA's about-face on the issue of on-court coaching.

"I'm big on tradition. I'm old.

"So I love the whole tradition of tennis and the one-on-one and problem-solving and what you're trying to do.

"But I think we're evolving as a sport."

Another change that won Cahill's backing was the 10-point tiebreaker being used in deciding sets for the first time at Melbourne Park this year.

Cahill said his teenaged children were typical of the younger generation who loved the fun and suspense that the elongated tiebreaks brought to the sport at the highest level.

"Coaching is a part of that as well," he said.

"Grand slams, put that aside, we have the four grand slams, and that's fine.

"But for the ATP and the WTA, we need to evolve and I think bringing coaching into those events is important.

"I know the WTA wants to do it, and they want to do it the right way.

" ... I think they can go further and do it more.

"If I was allowed to coach today, you'd be surprised how little coaching the coaches will do if they're allowed to do it.

"The reason why probably a lot of it goes on at the moment is because you're not allowed to do it so you're trying to get the sneaky coaching message across."

Australian Associated Press