Australia have called up the uncapped Glenn Maxwell and retained batsman Usman Khawaja in their squad for the third and final Test against Sri Lanka, which gets underway in Sydney on 2 January.

Maxwell has replaced fellow all-rounder Shane Watson, who has been sidelined by a calf injury sustained during the second Test in Melbourne, while Khawaja has been kept as cover for batsman Michael Clarke.

"Shane is out of the Sydney Test and Glenn comes into the squad as a replacement for Watson. The other person on standby is Usman, for me once again. I have got a bit of extra time now, winning this game in three days, to give myself every chance to be right for Sydney and I'm really confident I'll be fit for Sydney," said Clarke.

"Maxwell comes into the squad as the all-rounder, so it is a squad of 13 and then we wait and see what the conditions are like in Sydney. So we've got options. If you think the wicket is going to spin you've got the option of Maxwell."

Clarke scored a century in second Test, which the hosts won by an innings and 201 runs to win the series, but nursed a problematic throughout - and is likely to be rested next week

Vice-captain Watson's absence, meanwhile, has raised questions as to who will lead the team if Clarke can't play. The veteran Michael Hussey is the leading candidate to stand in as captain, while occasional limited-overs vice-captain David Warner is next line.

"I haven't had that conversation with the selectors, not to say they haven't thought about it, I'm sure they have. But I haven't. I don't know the answer to that question," added Clarke.

"I don't think my hamstring has got worse, that's for sure. The thing with my injury, it's about how you pull up as well. I really need to assess over the next 24 to 48 hours how I pull up, continue with my strength programme, continue with my maintenance work to make sure I'm 100 percent right for Sydney."

Squad: Michael Clarke, Jackson Bird, Ed Cowan, Phil Hughes, Michael Hussey, Mitchell Johnson, Usman Khawaja, Nathan Lyon, Peter Siddle, Matthew Wade, David Warner, Mitchell Starc, Glenn Maxwell.