This wasn't part of the plan. Little more than a fortnight into their home World Cup and already England are already playing what is effectively knock-out rugby against Australia.
Anything less than a win will realistically obliterate England's hopes of progressing into the World Cup knockout stage, making them the first tournament hosts to fail to do so.
Stuart Lancaster has handed Jonathan Joseph and Ben Morgan a return to the starting line-up and kept Owen Farrell at fly-half, while Australia coach Michael Cheika has made 14 changes from the side that thrashed Uruguay earlier this week.
The Wallabies have the experience
Michael Cheika may have referred to Australia's coaching staff as "babies", but his starting XV on Saturday at least has experience on its side with a higher average number of caps than England's. For the second successive weekend, Lancaster's men head into a big match with less experience of international rugby than their opposition.
- Average caps: England 29.7 - 48 Australia.
Dan Cole is the only player in the England team with more than 50 caps. In contrast, Australia's includes seven players to have crossed the milestone.
And age is also on the Aussies' side
- Average age: England 26.5 - 27.4 Australia.
Australia have the weight advantage in the scrum
- Weight of scrum: England 896kg - 913kg Australia.
Scrummaging has traditionally been a weak point for the Wallabies and such was England's forward dominance when the two sides met a year ago, coach Michael Cheika sacked forward coach Michael Blades.
The lessons of legendary Argentinian hooker Mario Ledesma were sought and he has been largely credited with bringing renewed steel and nous to the pack.
Stuart Lancaster has a winning record against Australia and coach Michael Cheika
- Lancaster's England 2 - 1 Australia.
Lancaster's first encounter with the Wallabies ended in defeat but since then his team have posted two consecutive victories. Last year's 26-17 win at Twickenham was the first and only time Lancaster has come head-to-head with Cheika.
Only the All Blacks and Springboks have a better visiting record at Twickenham
- Head-to-head at Twickenham: England 13 - 9 Australia.
Home advantage is on England's side, but Australia have one of the best records at Twickenham for a visiting team having won 41 per cent of their games against England at the stadium - only South Africa (58 per cent) and the All Blacks (75 per cent) have a better record.
England have won their last three World Cup meetings with Australia
- Head-to-head at Rugby World Cups: England 3 - 2 Australia.
Australia won the first two World Cup meetings between these two sides but since then the spoils have been England's with wins in the 1995 and 2007 quarter-finals and, most memorably, the 2003 final in the Aussies' own backyard.