Scott Staniforth may be the third Australian sent home from the World Cup with his shoulder and Stephen Larkham's knee, forcing Wallabies selectors to seriously consider another backline replacement.

Key reserve Staniforth has been ruled out of Saturday's high-pressure World Cup quarter-final against England in Marseille due to bad bruising to his joint.

The 29-year-old three-quarter joins Larkham on the sidelines as the veteran playmaker resumed running in Tuesday in a positive sign.

But the serious doubts over Larkham's twice-operated knee, which did pull up tight, will see the three-man selection panel decide after the quarter-final whether to call for a third replacement back.

With Australia badly lacking depth at inside centre, Connolly admitted the loss of Staniforth was a blow, particularly to the balance of his bench.

"He'll be out this weekend and we'll make a decision on his future at the tournament after Saturday," he said.

"Scott's important to us because of his flexibility, being able to play 12 and on the wing which helps our bench a great deal. He is a loss."

Larkham's light run at Stade Luminy was his first since initially aggravating his right knee on September 14.

The goal is for him to resume full team training next Tuesday to be available for a possible semi-final clash with New Zealand in Paris.

"Stephen ran pretty well yesterday," coach John Connolly said.

"He pulled up a little tight afterwards.

"He got up to a great pace but pulling up was a bit of a problem where he could feel it."

"If he gets through this week, he'll train again today and run again later in the week, by next Monday we'll have an indication of exactly where he sits.

"And that could impact, if we're still here next Monday, on what replacement we bring in if Scott's out."

Western Force centre Ryan Cross would be the favourite to replace Staniforth as he was considered when Morgan Turinui was chosen to replace No.8 David Lyons this week.

Turinui was the second late Wallabies call-up after Cameron Shepherd replaced Mark Gerrard (knee) at the start of the tournament.

New scan results confirmed Staniforth suffered no more than deep bone bruising when hit hard by Adam Ashley-Cooper's knee in a botched switch move against Fiji two and a half weeks ago.

There are few surprises expected when Connolly names his starting team on Wednesday but there is much interest in the composition of his bench.

Staniforth has been a regular this year due to his flexibility and No.12 Matt Giteau's use as a second-half halfback.

Giteau's versatility has allowed the selectors to take a 5-2 forwards-backs reserves split but the desire to leave him at inside centre next to rookie Berrick Barnes is more likely to see a conventional 4-3 split.

If that occurred, Sam Cordingley, Julian Huxley and leading tournament try-scorer Drew Mitchell - who is likely to be tipped out of his wing spot by Adam Ashley-Cooper - would be the backline reserves.

In the forwards, Hugh McMeniman has the inside running on Mark Chisholm and Stephen Hoiles on Phil Waugh.

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