As the No.1 ranked player in the world and still engaged in world sport's biggest rivalry with the No.2 seed and defending Australian Open champion Roger Federer, the 31-year-old Spaniard remains the star attraction.

Merely hopeful he can overcome the mental battle that comes with entering a grand slam with a nagging knee injury, he is keen for talk about his chances to remain realistic.

"Everyone starts from zero. I start from zero again," Nadal said.

"I hope to be healthy and competitive, and [the] most important thing ... I hope to enjoy tennis one more year."

If he ends the fortnight resuming his epic battle with Federer everyone will be satisfied regardless of whether he wins or not.

But that outcome is a long way away and Nadal is experienced enough to know that looking beyond his opening-round opponent, veteran Victor Estrella Burgos, is folly even though he should account for the No.81 ranked opponent without too much trouble.

What Nadal does know is that danger lurks everywhere in the shadows beyond the spotlight that shines on himself and Federer.

The No.3 seed from Bulgaria Grigor Dimitrov still finds himself ruing the opportunity he missed to beat Nadal at the Australian Open last year when he went down in the semi-final in five sets.

"I've learnt so much from that match. There's so many, like, bittersweet memories from it. It kind of set up a great year for me," Dimitrov said.

Another victim of Nadal over five sets at the Australian Open last year was emerging 20-year-old German Alexander Zverev who went down to Nadal in the third round.

He declared on Saturday that his goal was to improve his grand slam performances in 2018 and he feels he is well placed to do so.

"I've showed on multiple occasions over the year that I can play and beat the best guys in the world," Zverev said.

It might explain why Nadal seemed on edge at the media conference, unwilling to declare himself ready for anyone, wary of what lay ahead.

He said there was no reason why Belgium's David Goffin couldn't push further than his previous best grand slam performance of a quarter final.

"If he is fresh, and I believe that he is, he's very complete player. He can fight for everything. He is a big, talented player. He has experience already playing big matches. And why not?" Nadal said.

"Why not?" is the question all the players are asking this year as they ponder the possibility of the winner being someone other than Nadal, Federer, Novak Djokovic and Stan Wawrinka who have shared the past 12 titles between them.

Djokovic's battles with an elbow injury and Wawrinka's knee injury make them outside chances of winning the tournament while Nadal has made no secret of his uncertainty as he returns from a niggling knee problem.

???Andy Murray has failed to overcome a hip injury that ruined the second half of his 2017.

Nadal indicated such a spate of injuries could not be overlooked and called on tennis officials to examine the reasons why so many players were battling to be fit at this time of the year.

"I am not the one to take decisions but when something is happening too often [there is] something we are not doing well," Nadal said.