Cricket Australia is scrambling to get Test squad members David Warner and Sean Abbott out of Sydney as concern grows about the city's coronavirus cluster.
Warner (groin) and Abbott (calf) had been recovering from injuries at home, aiming to prove their fitness for the Boxing Day Test.
The prospect of border closures prompted CA to take urgent action, wanting the entire enlarged Test squad to be in the same place at the same time.
Warner and Abbott were expected to fly to Melbourne on Saturday, earlier than expected.
Abbott is unlikely to debut in this series, given fellow reserve pacemen James Pattinson and Michael Neser seemingly sit above him in the pecking order.
Warner will walk back into Australia's XI when fit.
The former vice-captain was hoping to return in the second Test against India at the MCG but Australia are likely to keep him on ice until the third Test.
"I'm not going to turn into an opener overnight ... I'll give it a good crack," makeshift opener Matthew Wade said on Thursday.
"Who knows if it's going to be for one or two Tests."
Mitchell Starc required an SA Health exemption to play days two and three of the first Test.
The paceman was able to get the green light from officials because he isolated at home prior to flying to Adelaide, as per CA's biosecurity protocols.
CA still plans on staging the third Test, which is slated to start on January 7, at the SCG.
But the governing body is monitoring the growing number of cases in the NSW capital closely as it mulls potential contingency plans.
There may be consecutive Tests at the MCG if the SCG is scratched, while Manuka Oval could also be in the mix.
A potential border closure between Queensland and NSW could be another hurdle for CA, given the fourth Test is being held at the Gabba.
There has been no impact on the BBL; Sydney Sixers and Sydney Thunder both headed into interstate hubs a long time ago.
However, border closures could force administrators to rejig the schedule for the Twenty20 competition.
CA is currently planning on games to be held in Brisbane, Adelaide, Perth, Sydney and Melbourne after the current hubs in Tasmania and Canberra.