Pace spearhead Ryan Harris will be given until Friday to prove he can carry an ongoing knee injury through the most important match of his career.

The 34-year-old Queensland quick battled soreness following Australia's victory in the second Ashes Test on Monday in Adelaide.

Mitchell Johnson has won consecutive man-of-the-match awards to skittle England's brittle batting, but the importance of Harris is massive.

Harris has claimed 32 wickets at 19.75 in 2013, second among Australians to pace partner Peter Siddle on 36 victims. Siddle has played 12 Tests to Harris' six.

Australia are yet to name a side for Friday's potentially Ashes-clinching Test, with pace duo Doug Bollinger and uncapped Nathan Coulter-Nile on standby.