MICHAEL CLARKE has received the backing of Australia's selectors to make his Test captaincy debut should Ricky Ponting fail to overcome his finger injury by Boxing Day.

Ponting was diagnosed with a minor fracture of the little finger on his left hand but is confident of playing in Melbourne. Selectors did not name a shadow player in an unchanged 12-man squad from Perth, but left the door ajar for an extra batsman to be drafted into the side ''should the [panel] determine the need for a standby player for Ricky Ponting''.

Full-time selector Greg Chappell hosed down reports suggesting he was not confident in Clarke's leadership capabilities. In a televised interview on Saturday, Chappell suggested there was no ready replacement for Ponting as Clarke is struggling with his batting form, but moved to clarify his statements yesterday.

''It was really in reference to Ricky Ponting and his captaincy as much as anything else, in defence of that,'' Chappell told ABC Radio. ''There's obviously a lot of discussion around that and what happens if the Ashes should stay with England.

''It was never my intention to suggest that Michael's not ready. I was … trying to be very careful not to make any suggestions against Ricky, and therefore … probably didn't speak clearly enough to get the message across. Michael is our next captain. Whenever that might be - we're hoping it's not for a while yet - we're happy with his skills as a captain.

''He's done it a number of times now in one-day cricket, his tactical nous is very good. There's no doubt he's ready for it. What I was alluding to was that when the handover comes we'd love him to be in the peak of his form so he hasn't got that problem on his shoulders as well. I certainly wasn't trying to suggest there was any problem there.''

Clarke has scored just 115 runs at an average of 23 this series - a far cry from last year's Ashes series, where he was Australia's leading scorer with 448 runs at 64 - and would be under enormous pressure were he called upon to make his Test captaincy debut amid questions over his form and susceptibility to the short ball.

But hope abounds that Ponting will be available for the all-important Boxing Day Test. Ponting, also in poor form with the bat having scored just 83 runs at 16.60 this summer, said he was in worse physical shape this time last year after West Indian quick Kemar Roach thundered a ball into his elbow in Perth, forcing him to wear extra protection against Pakistan in the next match.

''I'll have to make that decision [on availability] closer to the game - probably the morning of the game is when I make a decision like that - but I honestly think with being a little finger on my left hand, it's probably not as significant as my top elbow was last year,'' he said.

''There was no doubt that I was hindered last year and, to tell you the truth, I probably learned a fair bit from that. So I'm not going to be silly and put myself ahead of the team, especially in such an important game. If I don't think I can function well, then I won't play. But if I feel that I can function and play somewhere near - I won't say how I've been playing [but] better than I have been playing - then I'll play the game.''

Chappell conceded Ponting's captaincy would be under threat should England retain the Ashes - which can be achieved with victory in either of the two remaining Tests.

''Watching him in the nets, he's batting well,'' Chappell said. ''Perhaps the pressure of this series [has affected him]. I think in his own mind he built it up as being a very important series.

''He hasn't had the mental freedom he needs, perhaps, to bat with the freedom we know he's capable of. Hopefully the win here in this Test match, removing some of that pressure might give him the freedom to go out there and play in Melbourne as we know he can.''

Asked if Ponting would be under pressure to retain the captaincy if Australia did not regain the urn, Chappell said: ''Yes it is, but not terminal.''

Spinner Michael Beer will be hoping to make his Test debut at the MCG, and while it is difficult to change a winning side, selectors will remember well last year's series when they defeated England with four quicks and retained the same XI for the decider at The Oval. That tactic backfired badly when the pitch offered turn from day one and England won the series. The team hierarchy later conceded they should have played a spinner.