Canberra's Nick Kyrgios at career crossroads ahead of Wimbledon, says John Newcombe

Newcombe says Kyrgios should be pulling out all stops to beat the in-form Jordan Thompson in their all-Australian first-round encounter on Tuesday. But, like most, Newcombe can't guarantee what to expect from enigmatic talent Kyrgios, who hasn't reached a grand slam quarter-final in four-and-a-half years.

Victory over Thompson would likely set Kyrgios up for a spicy showdown with Nadal on Thursday, with Spain's 18-time major champion to begin his campaign against Japanese world No.258 Yuichi Sugita.

Kyrgios versus Nadal is the showstopper that, apart from Thompson camp, the entire tennis watching world yearns. The two have traded barbs all year, with Kyrgios branding Nadal "super salty" and the Spaniard accusing the Canberran of lacking respect.

But asked where Kyrgios's tennis and head were entering his sixth Wimbledon tilt, Newcombe said: "About where his ranking is. You don't know. You wouldn't know what was going to happen, so it's anybody's guess. I would imagine that he would see that draw and he would bust his guts to beat Jordan because he fancies himself against Rafa, especially on grass. He seems to play his best tennis when he's got nothing to lose. It could be an interesting match after all the talk."

Unseeded at the All England Club for the first time since 2014, when he upstaged Nadal as a 19-year-old on debut, Kyrgios is at a career crossroads, Newcombe said.

"He's been at one for a few years," said the former world No.1 and triple Wimbledon champion.

"He got his ranking to 13 a couple of years ago and now he's 43. I mean, that sort of speaks for itself. He's 24. He should be reaching his peak."

Thompson is certainly reaching his peak.

After charging to the final in Hertogenbosch and then the semi-finals this week in Turkey, the 25-year-old sits just one spot below Kyrgios at a career-high No.44 in the world. But Thompson knows he'll need to sustain his stellar grass-court form to deny Kyrgios a grudge match with Nadal.

"I don't want to let him get past me but I've got a job on my hands," he said.

"He's got an incredible serve. It's very unreadable and I've got to do everything in my power to try and just get it back into play. Then I've got to look after my own serve, so it's going to be a big task."

Meanwhile, Ashleigh Barty is playing down her status as Wimbledon title favourite as she enters uncharted waters as the world No.1, top seed and newly crowned French Open champion. Barty's spectacular rise on the back of a tour-best three titles and a 12-match winning streak has vaulted the Australian to the top of betting markets.

But, true to form, the understated Queenslander is playing down the hype.

"I don't know if I'm the favourite for Wimbledon. I think I need to try and get through this first round first and foremost," Barty said ahead of her championship opener against world No.43 Zheng Saisai on Tuesday.

"Saisai has incredible abilities to match up on a grass court. She has done well here in the past. She has got a good slice backhand, the kick serve that will react well off the courts. She loves playing on the grass courts. It's a tough first-round match, one that I know I'll have to be ready for. That's kind of the perfect start for me, trying to make sure I'm really switched on for that first-round match, trying to do the best that I can."

Barty said she was ready to go after arriving at the All England Club under a fitness cloud following her withdrawal from the Eastbourne International to rest bone stress in her over-used serving arm.

"Yeah, it's been good. It's been a really good couple of days," she said.

"It was nice to stay off the court for a few days, started hitting again on Thursday. As far as we're going, everything has kind of worked out well with monitoring our loads, all those kind of things. So feeling good."

Bidding to become Australia's first Wimbledon champion since Lleyton Hewitt in 2002 and first Aussie woman since Evonne Goolagong Cawley in 1980, Barty is in a loaded top quarter of the draw alongside four former world No.1s and four former champions - including Williams and Kerber.

But she is focusing solely on Zheng.

"I haven't looked at the draw," said Barty, dismissing the notion that the grass-court slam boasted less contenders than other majors because of the difficult surface.

"There are obviously girls that are more comfortable on grass courts, girls that have played on them a lot more, but there are still always going to be some upsets rankings-wise. There are always going to be some results that people don't expect, but that's the nature of the beast. That happens every single tournament, whether on hard court, grass court or clay. That happens every tournament."

Victory over Zheng would progress Barty to a second-round match on Thursday against either former French and US Open champion Svetlana Kuznetsova or Alison Van Uytvanck.