Australian Open chief Craig Tiley said Wednesday he was confident that Rafael Nadal will play in Melbourne despite testing positive for Covid-19, as fresh doubts emerged over Novak Djokovic.

Spanish star Nadal said on Monday that he tested positive after returning home from an exhibition tournament in Abu Dhabi and was experiencing "some unpleasant moments".

While the 20-time Grand Slam champion said he was examining all his playing commitments, Tiley believes Nadal will be sufficiently recovered to chase his second Australian Open title in January.

"I'm confident Rafa will be here," the tournament director told reporters in Melbourne.

"Players that are testing positive now will complete a period of time until they are no longer infectious and they'll be fine."

World number one Djokovic, who has won nine of his 20 Grand Slams at Melbourne Park, remains in serious doubt over his refusal to confirm if he has been vaccinated.

The 34-year-old has been named on the tournament entry list but his father Srdjan reportedly said his participation is still not guaranteed.

Tiley said "a small percentage" of unvaccinated players and staff would be granted medical exemptions at the Australian Open, but their identity was protected by strict privacy protocols.

Rafael Nadal tested positive for Covid-19 on his return to Spain from Abu Dhabi
Rafael Nadal tested positive for Covid-19 on his return to Spain from Abu Dhabi AFP / Giuseppe CACACE

He was not aware of any players informing organisers they had an exemption.

"If Novak shows up at the Australian Open, he'll either be vaccinated or he'll have a medical exemption," Tiley said.

"Medically, he doesn't talk to anyone about it -- I'm not going to ask Novak that, it's none of my business."

Any indication Djokovic had received a vaccination exemption would likely prompt a furious public backlash in Melbourne, which has endured long periods of lockdown in a bid to contain the virus.

The Australian Open field has already been ravaged by injuries, with superstars Serena Williams and Roger Federer out, along with Jennifer Brady, Karolina Pliskova, Bianca Andreescu and Karolina Muchova.

Former US Open champion Dominic Thiem is struggling to return from an injury-enforced layoff, while rising star Emma Raducanu and Olympic champion Belinda Bencic have tested positive for Covid-19.

Tiley said there was still enough time for players with coronavirus to recover for the event, which begins on January 17.

"If you're going to test positive and you want to play the Australian Open, your timing would be now," he said.