England suffered a major injury blow just two days before their World Cup quarter-final against Australia when centre Andy Farrell was ruled out with a strained right calf muscle.

The former Great Britain rugby league captain, who was recalled to the side after being dropped following the record 36-0 defeat by South Africa last month, underwent an MRI scan this morning.

As a result England have drafted 36-year-old London Irish centre Mike Catt into their starting line-up.

Catt , who is set to win his 73rd cap, has not featured in the tournament since England suffered a record 36-0 World Cup defeat against South Africa three weeks ago.

But his experience and big-match temperament means that he will be crucial to England's cause as they target a semi-final appointment with New Zealand or
France in Paris next week.

"I?ve always said never say never and it?s a chance for me to go out there and perform," commented Catt following his selction.

?I?ve always enjoyed games against Australia, I?ve played against them 10 times now, and I?m sure it?ll be a great occasion.?

Ashton appeared to face a choice between Catt, Olly Barkley and Newcastle's Toby Flood for the number 12 shirt.

Barkley has subsequently failed to recover from a dead leg picked up in training this week and Flood has taken his place on the bench.

Australia are firm favourites to end England's reign as world champions at Stade Velodrome, and therefore avenge their 2003 final defeat in Sydney.

The loss of Farrell is a cruel blow both to the player and his team, with Ashton having selected him for the "direct approach'' he would have brought.

Farrell's injury denies him a chance to play in the biggest game of his union career since switching codes and joining Saracens.

His progress in the union ranks has been repeatedly stalled by injury problems, seriously hampering his progress with club and country.

The 32-year-old made his England debut against Scotland during last season's RBS 6 Nations, while he produced a try-scoring display during Friday's victory over Tonga.

England's World Cup campaign has been dogged by injuries, with the likes of Barkley, Jonny Wilkinson, Jason Robinson and Mark Cueto among those who suffered
setbacks at various stages.

Barkley would offer England a considerable kicking option alongside Wilkinson in the number 12 jersey against Australia, yet Catt might be more suited to Ashton's plan.

The identity of Farrell's replacement will be revealed at a scheduled lunchtime press conference in Marseille tomorrow.

Full-back Jason Robinson, meanwhile, has recovered from a hamstring injury sustained against South Africa last month, with Josh Lewsey moving to the wing instead of Mark Cueto.

Three switches in the pack see hooker Mark Regan preferred to George Chuter, World Cup captain Phil Vickery back at tighthead prop for Matt Stevens and lock Simon Shaw replacing Steve Borthwick.

Flanker Lewis Moody wins his 50th cap in an unchanged back row after the Tonga clash, which means Lawrence Dallaglio stays on the bench.

Barkley pays the price for a defensively-suspect display against Tonga, moving to the bench, where he is joined by Chuter, Stevens, Dallaglio, Joe Worsley, Peter Richards and Dan Hipkiss.

Robinson limped off during England's record 36-0 World Cup loss to the Springboks 19 days ago, nursing an injury that forced him to miss the Samoa and Tonga games.

But he now returns for his 49th cap in what would be a final Test appearance before retirement if England lose.

Cueto, meanwhile, has been struggling to overcome a calf muscle injury, but the versatile Lewsey is no stranger to wing duties.

Regan offers greater experience than Chuter, which might have clinched his selection, and Shaw - arguably England's form World Cup forward - returns to partner Ben Kay in the second row.

Robinson, Lewsey, Vickery, Kay and fly-half Jonny Wilkinson are all starting line-up survivors from the 2003 World Cup final in Sydney, when England beat the Wallabies 20-17.

Saturday's victors will secure a semi-final clash against tournament favourites New Zealand or host nation France in Paris on October 13.

England head coach Brian Ashton originally explained the inclusion of Farrell ahead of Barkley was down to leadership and the threat England expect he will pose to the Wallabies.

Ashton said: "For this game we need the direct approach Andy Farrell brings. He has come on a couple of times now as a replacement and done, I feel, particularly well.

"He has been a threat to opposition lines in terms of his kicking game, defensive work and general leadership and game management.

"That is what we are looking to bring to the game on Saturday.''

Ashton put Vickery's recall down to the need for experience in the scrum.

"It is important we get the most experienced players in the front five on the field this week. It will be a massive battle area,'' said Ashton.

"The changes in the front row signify we are looking for a strong emphasis scrummaging wise at the weekend.''

Ashton admitted he thought Robinson had played his last Test match when he limped off in the defeat to South Africa.

"Jason Robinson is an outstanding player. Everyone knows that. The Australians have commented on that and we are delighted he is fit and available,'' said Ashton.

The World Cup's leading try-scorer Drew Mitchell has been dropped to the bench for the clash in Marseille.

Mitchell has scored seven tries in four appearances but Wallabies head coach John Connolly has opted to start with Adam Ashley-Cooper on the right wing.

Australia captain Stirling Mortlock returns to outside centre after recovering from a shoulder injury which kept him out of the pool victories over Fiji and Canada.

Rookie fly-half Berrick Barnes and scrum-half George Gregan return to the side after being rested for the Canada game.

Connolly said the need to play a "slightly tighter game'' prompted the selection of the versatile Ashley-Cooper, who starred on the wing.

But he said: "It was a points decision. Adam did very well in the All Blacks game (scoring a try in Australia's win). Drew has also done very well this tournament.''

Connolly insists England are one of the Wallabies' major World Cup threats and told his side they must improve for Saturday's Marseille showdown.

"England are a very dangerous team. Their set-piece has been their cornerstone for many years and they have incredible speed out wide and a number 10 (Jonny Wilkinson) who steers them around exceptionally well,'' he said.

"When you look at our results through the pool games you would have to say we're pretty happy with where we're at.

"But we're very conscious that we have to improve considerably on that to go any further in the tournament.''

Key Battles:

JASON ROBINSON (England) v CHRIS LATHAM (Australia)

England full-back Robinson produced what head coach Brian Ashton described as one of the tournament's finest individual displays against South Africa three
weeks ago, but it all ended in agony as Robinson limped off with a hamstring injury and the world champions lost 36-0.

Robinson, England's 2003 World Cup final tryscorer, has now made a complete recovery and he returns as England's most potent attacking option, but the
brilliant Queenslander Latham possesses pace, power and finesse in abundance and he will hurt England if they give him an opportunity.

JONNY WILKINSON (England) v BERRICK BARNES (Australia)

Four years after Wilkinson kicked the World Cup-winning drop-goal that broke Australian hearts, Newcastle's finest plans a repeat performance as England's
playmaker and matchwinner-in-chief. He also needs just six points to overtake Gavin Hastings as the all-time top World Cup pointscorer.

While England are relieved to have Wilkinson fully fit following a succession of injury troubles, Australia will look for another masterclass from 21-year-old Barnes, who continues in the number 10 shirt vacated by an injured Stephen Larkham. Barnes exudes confidence and quality, but no team has seriously tested him yet in this World Cup.

ANDREW SHERIDAN (England) v GUY SHEPHERDSON (Australia)

Sale Sharks prop Sheridan's one-man wrecking job on the Australian front row at Twickenham two years ago left the Wallabies suffering from severe mental
scarring. The set-pieces are again an area where England will look to make their presence felt, with 6ft 4in, 19-stone Sheridan spearheading the push for
physical supremacy.

Wallabies forwards coach Michael Foley has overseen a considerable improvement in the Australian front five since that bleak November afternoon, and ACT
Brumbies tighthead Shepherdson is the player entrusted with holding Sheridan. It could prove the biggest examination of his Test career.

LEWIS MOODY (England) v GEORGE SMITH (Australia)

"Mad Dog'' Moody, as he was affectionately christened during an England press conference earlier this week, wins his 50th cap on an occasion when he must
again adopt the fearless, selfless attitude he brings to every game he plays in.

Physically battered after launching his body through the pain barrier against Tonga last week, the Leicester flanker will keep a close eye on Wallabies
fly-half Barnes and look to win a mouth-watering battle with Australian openside Smith, whose ability at securing possession on the floor is perhaps peerless in world rugby.

Australia: C Latham; A Ashley-Cooper, S Mortlock (capt), M Giteau, L Tuqiri; B Barnes, G Gregan; M Dunning, S Moore, G Shepherdson, N Sharpe, D Vickerman, R Elsom, G Smith, W Palu.

Replacements: A Freier, A Baxter, H McMeniman, S Hoiles, P Waugh, J Huxley, D Mitchell.

England: J Robinson (unattached); P Sackey (Wasps), M Tait (Newcastle), M Catt (London Irish), J Lewsey (Wasps); J Wilkinson (Newcastle), A Gomarsall (Harlequins); A Sheridan (Sale Sharks), M Regan (Bristol), P Vickery (Wasps, capt), S Shaw (Wasps), B Kay (Leicester), M Corry (Leicester), L Moody (Leicester), N Easter (Harlequins).

Replacements: G Chuter (Leicester), M Stevens (Bath), L Dallaglio (Wasps), J Worsley (Wasps), P Richards (London Irish), T Flood (Newcastle), D Hipkiss (Leicester).

Referee: Alain Rolland (Ireland).

Touch judges: Paul Honiss (New Zealand) and Nigel Owens (Wales).