As Tennis Australia continues delicate discussions with government officials to allow unvaccinated players to contest the Open from January 17-30 in Melbourne, plans to stage warm-up tournaments elsewhere around the country are also coming together.

With most state borders reopening, TA is confident all lead-in events won't have to be held at Melbourne Park as they were this year because of the pandemic and biosecurity bubble requirements.

Significantly, the ATP Cup - which was reduced from 24 teams to 12 this year - is expected to return to Sydney, with Adelaide and Brisbane also potential hosts for the group stages.

Perth was a co-host in 2020 but, with Western Australia's staunch border closure remaining in place, there'll be no return there until at least 2023.

The Adelaide International, won by Australia's world No.1 Ash Barty the last time it was contested before the Open in 2020, is likely to return to its traditional place on the calendar and also feature a men's event.

After being held in Doha and Dubai this year, Australian Open qualifying will return to Melbourne Park in 2022.

While the summer program is beginning to take shape, TA, the WTA and ATP are feeling the heat over the emergence on Monday of a leaked email from the WTA to its Players' Council saying unvaccinated players would be free to compete at the Open provided they completed a two-week stint in quarantine.

In reaching this year's women's final, American Jennifer Brady proved it was possible to be competitive at the season's first grand slam even after enduring a fortnight holed up in a hotel room without being able to train.

But Victorian premier Daniel Andrews is among the government leaders applying the pressure to the WTA and ATP to make it mandatory for players to be fully vaccinated before being granted entry to Melbourne Park in 2022.

Andrews says if fans must be double-vaxxed, then so should the players.

"You try getting into the US ... most of Europe, really, so many different parts of Asia if you haven't been vaccinated," Andrews told ABC radio.

"Like, you're just not getting a visa. Why would that be different here?

"I don't think it's too much to say, if you want one of those visas and you want to come here, then you need to be double-vaxxed.

"All the people who are watching the tennis at the Australian Open, they're going to be double-vaxxed, all the people that work there are going to be double-vaxxed.

"It stands to reason that if you want to get into the country to be part of that tournament, then you should be double-vaxxed as well."

Open boss Craig Tiley estimates around 80 per cent of players are fully vaccinated, with the number said to be rising.

But world No.1 Novak Djokovic, who would be chasing a 10th Open title should he return to Australia, and the second-ranked 2020 runner-up Daniil Medvedev are among those yet to reveal their vaccination status.

Andrews says the decision on whether to let unvaccinated players into the country ultimately rested with the Commonwealth government.

But if unvaccinated international players are allowed into the country, they still face another hurdle under Victoria's vaccine mandate for authorised workers.

Professional sportspeople, including tennis players, are subject to the mandate, which requires all workers to be fully vaccinated by November 26 to do their job on site.

It means the ball could be in the Victorian government's court to make the final decision

Australian Associated Press