Australia number eight David Lyons will play no further part in the World Cup after breaking his leg during the Wallabies' 37-6 win over Canada on Saturday.
Lyons limped off the field early in the second half after a heavy tackle and X-rays later revealed he had fractured his left fibula. "The normal recovery period for a fractured fibula is between three and four months," Australia team doctor Martin Raftery said in a statement.
"It would certainly be impossible for him to return to play during the World Cup."
Wallabies coach John Connolly said the team management had not decided on a replacement yet but were considering calling in an extra back as cover for injured flyhalf Stephen Larkham, who has already been ruled out of the quarter-final against England after undergoing two minor knee operations. Berrick Barnes, 21, has been given the task of marking Jonny Wilkinson next weekend and Connolly said Kurtley Beale may be added to the squad as a back-up in case Larkham doesn't recover in time for the semi-finals, should Australia make it.
"It's possible (Lyons' replacement) won't be a forward but it may be an inside back," Connolly told reporters on Sunday.