Injury clouds over Shane Watson and Ryan Harris threaten to deny Australia the rare opportunity to complete an Ashes clean sweep over England with the same line-up for five straight Tests.

Australia moved four-nil up in the series yesterday with a commanding eight-wicket win at the MCG, but Watson’s groin strain and Harris’s knee and foot complaints have left selectors pondering possible changes to the bowling attack for the fifth and final Test starting in Sydney starting on Friday.

All-rounder James Faulkner could be poised for a recall if Watson is ruled out, while left-arm paceman Doug Bollinger and uncapped Nathan Coulter-Nile are also be in the frame if Harris is rested.

‘‘If he is not fit, he won’t play,’’ Australia coach Darren Lehmann said yesterday of Harris, who took 2-81 in Melbourne including 10 wicket-less overs in England’s second innings.

‘‘I would say he is doubtful but until we see the medical staff and see how he recovers.’’

Harris has fought an ongoing battle with knee soreness and the 34-year-old has also suffered from foot blisters in Melbourne.

‘‘It’s everything with him.

‘‘He is a valuable bowler so we won’t take any risks,’’ Lehmann said.

While No3 batsman Watson is averaging 41.85 in the series, Lehmann says he wants five bowlers in the side to share the load.

‘‘He batted very well today,’’ Lehmann said. ‘‘But he’s an all-rounder. He has to bowl.’’

Australia skipper Michael Clarke said it was a special win to come from behind at the MCG in the Fourth Test, scoring 2-231 to reach their victory target before tea on day four.

Chris Rogers (116) and Shane Watson (83 not out) added 136 for the second wicket as England fell to pieces in the field. Captain Alastair Cook dropped two catches at first slip.

Tearaway quick Mitchell Johnson was named man of the match for the third time in the series, lifting his tally of victims to 31 with hauls of 5-63 and 3-25.

England had failed to take their advantage after claiming a 51-run lead on the first innings.

The tourists crashed from 5-173 to be all out for 179 in their second innings on Saturday.

David Warner was out for 25 on Sunday at 1-64 and Rogers departed at 2-200.

Rogers raised both arms in a salute to the crowd of 38,522 after reaching his second hundred of 2013.

Clarke said Rogers seemed to thrive on the pressure of holding his spot in the side at the age of 36.

After making the surprising move to bowl first, Australia found themselves in a spot of bother after day two at 9-164 in reply to England’s 255.

Clarke said his side had proved their knockers wrong.

‘‘The fact that a lot of people thought we would come here complacent and not have the same willpower to continue to play the same way as in the first three Tests,’’ he said.

‘‘But also for the first time in this series we found ourselves behind in the game. We’ve been able to turn that around.’’

Australia’s domination of the series has placed Cook under pressure to retain the England captaincy and the opener said he’d take it on the chin if selectors felt there was a better candidate to lead the side.

Cook is a veteran of England’s 2006-07 side which lost 5-0 in Australia.

The only other Ashes sweep in a five-Test series came when Australia thumped England 5-0 down under in 1920-21. - AAP