Australia was picked over New Zealand to host the coronavirus-affected Rugby Championship on Friday, but the pandemic may prevent world champions South Africa from even taking part.
The four-way international tournament, which also involves Argentina, was originally scheduled to begin in August.
But the COVID-19 pandemic forced a rethink and the decision to play in only one nation, given border restrictions. Twelve matches will now played between November 7 and December 12.
All rounds, bar one in Queensland, will be in the southeastern state of New South Wales, where Sydney is the capital.
But South Africa's participation is in doubt as the country continues to battle coronavirus, with all sporting competition there currently suspended.
"The Springboks' participation will be dependent on the relaxation of that suspension as well as overcoming a number of other logistical challenges including the opening of international air borders," said SANZAAR chief executive Andy Marinos.
The southern hemisphere governing body previously said New Zealand was the preferred option to host the tournament due to its success in containing the virus, but after months of negotiations Australia pipped it to the post.
Marinos said Australia ultimately got the nod "based on government-required quarantine protocols (for entry and training prior to the tournament) and commercial underwriting".
"The Rugby Australia submission was the most desirable and workable in terms of tournament logistics for the essential pre-tournament preparation period and the six-week tournament itself," he added.
- New Zealand 'disappointed' -
Under Australian quarantine conditions, teams will be able to train together in large groups while in mandatory 14-day isolation.
This was seen as important given neither South Africa nor Argentina have resumed competitive rugby since the pandemic brought sport to a halt earlier this year.
Australia and New Zealand are match-fit after playing domestic Super Rugby competitions.
New Zealand's case was also not helped by a second wave of Covid-19 in its largest city Auckland, although it is now under control and a lockdown has been lifted.
While Australia's Victoria state is also battling a second wave, New South Wales and Queensland are only seeing a handful of new infections.
To compensate for missing out, the All Blacks' two Bledisloe Cup Tests against the Wallabies, which were due to be played in Australia in October, will now be in New Zealand.
Fans are expected to be allowed in Australia. Under current New South Wales rules, venues can be up to a quarter of normal capacity or 10,000 spectators, whichever is less.
"We're obviously disappointed at the decision to not have New Zealand host the tournament, but we understand and accept it," said New Zealand Rugby chief Mark Robinson.
"We worked incredibly hard behind the scenes with a whole range of stakeholders, including SANZAAR and the New Zealand government, to ensure we were ready and able to host the Championship and we felt we were."
Fixture details will be released over the coming weeks.
"We will now knuckle down to make these plans a reality," said Rugby Australia's interim chief Rob Clarke, who added that the Wallabies' postponed Tests against Ireland and Fiji that were scheduled for July will no longer go ahead in 2020.