Farrell's World Cup could be over after suffering a calf strain
England v Australia
Stade Velodrome, Marseille
Saturday, 6 October
Kick-off: 1400 BST
Live on BBC Radio 5live and the BBC Sport website
England centre Andy Farrell has been ruled out of the World Cup quarter-final against Australia in Marseille on Saturday.
The 32-year-old former Great Britain rugby league captain injured his right calf muscle in training on Wednesday.
England will not name his replacement until Friday, with Olly Barkley, Mike Catt or Dan Hipkiss set to come in.
Barkley is the favourite but he picked up a dead leg in training on Wednesday, although he says he is recovering fast.
Barkley played inside-centre in England's last two pool games, against Samoa and Tonga, but came off after 60 minutes in the Tonga game and was replaced by Farrell.
Barkley and Leicester centre Hipkiss have both been named on the bench for Saturday's match, but England coach Brian Ashton could opt for the greater experience of 2003 World Cup winner Catt.
The 36-year-old could come in as a straight replacement to partner Mathew Tait in the centres or he could take over the fly-half jersey, with Jonny Wilkinson moving to inside centre.
Hipkiss is more of an outside centre and his call-up would lead to a re-jig of the midfield.
Wilkinson, himself no stranger to injury, said Farrell's strength of character would be missed.
"It's not an ideal scenario for a team to have to announce a player not making a game. It's tough for Andy himself," he said.
"Andy's had a fantastic tournament so far, off the field especially, what he's brought to the squad in terms of solidity and consistency in attitude and his performance against Tonga summed it up.
"It is a disruption but the strength and depth in the squad means we can overcome that quickly and get on with it."
Former Wigan rugby league star Farrell has endured a frustrating time since switching codes in a move funded by Saracens and the Rugby Football Union in 2005.
He missed his entire first year in union because of injury and was briefly tried at flanker before being moved to the centre position.