The 35-year-old Spaniard will be chasing a record 21st Grand Slam crown when he begins his Melbourne title charge on Monday against the 66th-ranked American Marcos Giron.

The draw could open up nicely for him with the grave uncertainty surrounding reigning champion Novak Djokovic, but Nadal said that he is not expecting too much of himself.

"I came here just with the clear goal to be back on the tour, that's the most important thing," said Nadal, who battled a foot injury for much of last year, ended his season in August and contracted Covid in December.

"Then if I am able to win matches, improving every single day, fantastic."

Nadal admitted that it had been hard at times to keep motivated because of the latest injury to dog a career that has brought him 20 Grand Slam crowns, level on the all-time list with "Big Three" rivals Djokovic and Roger Federer.

"First thing, be healthy. Then hold the passion, that sometimes is difficult when you are going through a lot of physical issues," he said.

"Last year and a half with my foot, I have been suffering a lot. I think I hold the positive attitude and the working spirit all the time. That's probably why I'm here today."

Nadal said that he felt unwell for about a week with the virus, but he seemed to be suffering no long-term effects as he won a Melbourne warm-up tournament for his 89th ATP singles title a week ago.

"In general terms, I feel happy. If you tell me that I am going to be in my position today one month ago, of course I will sign without a doubt the paper saying that I will be in this position," he said.

"Just enjoying the practices and be back and feel myself again a professional tennis player. I'm playing some good tennis."

Nadal admitted it remains to be seen how he will hold up in five-set matches, but he is delighted to be able to compete and fight on.

"I want to give myself a chance to keep enjoying this beautiful sport, to keep fighting for the things that I have been fighting for the last 16 years," he said.

"I really believe that if I am healthy and if I am able to play weeks in a row on the tour, have more or less a normal calendar, I will have my chances to be in an important position on the tour and give myself chances to keep fighting for important things."