Peter Handscomb may yet be dropped from the XI that defeated the tourists in Perth if Australia decide to promote allrounder Mitch Marsh in Melbourne.

But Handscomb, likened to a "lamb to the slaughter" by Shane Warne after a terrible lbw dismissal in the second Test, has been retained in the squad.

Reserve paceman Peter Siddle also remains part of the squad but will be on drinks duty at the MCG and SCG unless Mitchell Starc, Josh Hazlewood or Pat Cummins suffer an injury.

Selectors have bucked recent tradition by making an early call and deciding to play a single spinner in Sydney.

Ashton Agar and Steve O'Keefe have been part of the SCG Test squad in recent years.

"We've made the decision to stick with the 13-person squad for the remaining two Test matches," chairman of selectors Trevor Hohns said.

"We believe it's important to keep this group together to build on the momentum we have established in Perth.

"We will regroup in Melbourne for the Boxing Day Test over the weekend, and we look forward to preparing for another tough challenge against the No.1 Test team in the world."

Captain Tim Paine suggested it's far too early to decide whether Australia will stick with the same XI they used in Adelaide and Perth.

"Conditions are going to be different at the MCG than they were here, and then in Sydney," Paine said.

"We will have to pick what we think is the best combination to win both of those Tests.

"If it's this XI, then great.

"But if we have to make some changes I am sure will talk about that at some stage."

The series, level at 1-1 following Australia's victory in Perth, continues at the MCG on Boxing Day.

Australia's squad will assemble in Melbourne on the weekend.

Australia's 13-man Test squad: Marcus Harris, Aaron Finch, Usman Khawaja, Shaun Marsh, Peter Handscomb, Travis Head, Tim Paine (capt), Pat Cummins, Mitchell Starc, Nathan Lyon, Josh Hazlewood, Peter Siddle, Mitch Marsh.

Australian Associated Press