Aussie great's warning for Nick Kyrgios as Australian Open approaches

Tennis great John Newcombe says firebrand Nick Kyrgios will have to "learn to zip it up" during the Australian summer given the ban hanging over his head.

Kyrgios will still be on his six-month ATP probation at the season-opening grand slam as part of the punishment from his meltdown during a match in Cincinnati in September.

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He faces a 16-week suspension and hefty fine if he steps out of line.

Newcombe said the pressure and intensity at Melbourne Park may make it tough for the 24-year-old to toe the line.

"I can't speak for him but if it was me it would be tough having that ban hanging over you. But I guess you've just got to learn to zip up," Newcombe said on Monday.

The seven-time grand slam singles champion said it was great to see Kyrgios welcomed back into the Davis Cup fold for last month's tournament in Spain.

But with Kyrgios forced to sit out his singles rubber in their heart-breaking quarter-final loss to Canada through injury, he feared he may not be up to five set tennis next month.

"I thought it was great that Nick played in the Davis Cup but it's a bit of a worry that he has recurring injuries - especially around where the muscles join the joints and that's going to be an ongoing problem for him it seems," Newcombe said.

"At the Davis Cup he'd only played four sets of singles and his shoulder started to play up again and when you've got an injury like that it's hard to go out and practise a lot.

"Leading into the Australian Open - five sets is a big ask for him."

Newcombe revs up rising star de Minaur

Speaking in Melbourne ahead of the Newcombe Medal, named in his honour, the 75-year-old also didn't expect to see Australian men's No.1 Alex de Minaur taste Open glory next year.

A rising star of the tennis world, de Minaur climbed up to world No.18 in the rankings in 2019 after winning three ATP titles and reaching the US Open fourth round.

But Newcombe thought the 20-year-old wouldn't win his first grand slam for another five years.

"After fighting back from injury he had a great second half of this year so 2020 looks like being really good for him," he said.

"He's a probable top 15 and hopefully top 12 or 10 as long as he can stay injury free as every question asked of him he's come up wit the right answers.

"But I can't see him contending in a grand slam the next 12 months, that's a little quick - I think he's a couple of years away from that.

"I would think Alex would be playing his best tennis around 25 or 26 years of age."