Nick Kyrgios has urged Rafael Nadal and Novak Djokovic to play at the Australian Open, saying it would be a "disaster" if the 'Big Three' were missing.
Swiss ace Roger Federer has already pulled out as he recovers from a knee injury and Nadal's plans are unclear after contracting Covid-19.
Djokovic is on the entry list for the first Grand Slam of the year, which begins in less than three weeks, but has refused to confirm if he has been vaccinated, casting doubt on whether he will turn up.
The dominant trio have won 20 Grand Slam titles each and Kyrgios said tennis still needs them, starting in Melbourne next month.
"I honestly don't know Novak's current situation with anything Covid-related or what he needs to play," Kyrgios told the Melbourne Age.
"I hope he's had a good Christmas and I hope he's able to play in the sport for as long as possible because I've voiced before I think Federer, Nadal and Djokovic need to be (playing).
"If all three aren't there, it's a disaster. It's an absolute disaster for the fans and the people that enjoy tennis.
"Yes, it's obviously a good opportunity for some of the younger guys to come through and make an impact, but as a whole, we do need them to be part of the sport."
Adding to the Australian Open woes, Dominic Thiem, who lost to Djokovic in a five-set classic in the 2020 final, said he would miss the event with a wrist injury.
Meanwhile, Russian world No 5 Andrey Rublev and Canada's Wimbledon semi-finallist Denis Shapovalov are also recovering from coronavirus, casting a shadow over their preparations.
The Australian Open starts at Melbourne Park on January 17.
Australia's Kyrgios, who has slipped to 93 in the world, has not played since the Laver Cup in late September, citing a knee injury, and said he was looking forward to performing again in front of his home fans.
"My knee is something that has been hindering my career for a while now, it's just something I had cleaned up last year and it feels good," he added. "I want to enjoy myself, I want to be happy, and that is it."