Clarke undecided on Melbourne Test

Australia captain and selector Michael Clarke put himself through a searching fitness test on Tuesday but is yet to decide if he'll lead the side in the Boxing Day clash with Sri Lanka.

Clarke suffered a hamstring injury during last week's first Test in Hobart but has made steady improvement in recent days, including batting and fielding sessions at the MCG on Tuesday.

'It's improving every day,' Clarke told a media conference.

'I did a fair bit of running today in the indoor nets. A decision can't be made today.

'I really need to wait and see how I pull up tomorrow morning.

'I'm still pretty positive I'll be right for tomorrow.

'I haven't run at a hundred per cent but I've certainly built up over the last three days.'

Young batsman Usman Khawaja, who has been out of the side for a year, is on standby for Clarke.

Tasmania paceman Jackson Bird will make his debut in place of injured quick Ben Hilfenhaus while Mitchell Starc has been rested and his fellow left-armer Mitchell Johnson returns to the lineup.

Australia lead the three-match series 1-0.

Likely team: Michael Clarke (capt), Ed Cowan, David Warner, Phil Hughes, Shane Watson, Mike Hussey, Matthew Wade, Mitchell Johnson, Peter Siddle, Nathan Lyon, Jackson Bird. (Note: Usman Khawaja is on standby for Clarke.)