The Wallabies have suffered a double blow ahead of their tour finale against England, losing in-form centre Tevita Kuridrani to injury and slumping to their equal lowest-ever ranking.
Kuridrani was hurt early in the second half of the weekend's 26-23 loss to Ireland in Dublin and tests have confirmed the 23-year-old suffered a low grade ankle injury.
The Fijian-born centre will remain with the squad in London this week but his unavailability for Sunday morning's match at Twickenham will hit Australia's hopes of avoiding their worst spring tour since 2005.
The Wallabies will head into the match with their pride dented further by slipping to fifth in the world rankings following back-to-back losses, with England climbing above them into fourth following a 28-9 win over Samoa.
It matches Australia's lowest position since the rankings were introduced in 2003.
Brumbies star Kuridrani has been arguably the Wallabies' form player in recent months, scoring in three of the past six matches and causing havoc in opposition defences with his power and pace.
Australia also lost to France.