The left-arm pace ace had scans to determine the extent of the heel problem that surfaced during the first innings of Australia's victory in Perth.

The crutches are believed to be a precaution to take the weight off Starc's bruised right heel. That Starc was able to complete the game has raised hopes he has avoided a more serious injury such as a fracture.

The injury is not believed to be related to the stress fracture that forced him home early from the Test tour of India and sidelined him again after the Champions Trophy.

With the Ashes won and a marquee four-Test series in South Africa on the horizon, selectors will be loathe to take any risks with Starc, who is the leading wicket-taker this campaign.

They would have little to gain and plenty to lose if Starc was to break down having been asked to do too much on what has traditionally been a batsman-friendly MCG strip, particularly in a dead rubber.

If Starc was to aggravate his heel issue, he would be racing the clock to be fit for the start of the series in South Africa in just over two months' time.

While he was upset to miss the Boxing Day Test in 2012, he played in last summer's feature and could also line up at his home Test if he misses out in Melbourne.

"We'll wait and see. It's the same 13, we'll make that decision when we get to Melbourne," coach and selector Darren Lehmann said.

Tasmania's Jackson Bird would come into the XI if Starc was ruled out. The Sydney-raised Bird is also a chance to play at the SCG if selectors opt to wrap Cummins in cotton wool at the end of a long series.

??????

While Steve Smith has taken man of the match honours in two of the three Tests, the ability of the big three quicks - Starc, Josh Hazlewood and Pat Cummins - to strike regularly has been a key in Australia's success.

The star trio, who have regularly hit speeds in excess of 140 km/h, have taken 45 wickets at 24 apiece to the 31 at 42.6 by England's quicks.

While Joe Root's seamers have been criticised for lacking the pace to have an effect in Australia, they have also had to contend with arguably the best batsman in the world - Steve Smith.

"Our fast bowlers have bowled very well," Usman Khawaja said. "When fast bowlers don't go as well sometimes the credit has to go to the batsman and vice-versa.

"You might have to give credit to Steve Smith, who is absolutely on fire. No one seems to be able to get him out. [Mitch] Marsh batted beautifully this game and Shaun the game before.

"Our batsmen have done the deed, made some runs and big runs and the English haven't been able to do that yet. Probably more credit to our batsmen than anything."