England head coach Stuart Lancaster will name his November squad on Wednesday, with the midfield having given him a big selection headache.
Injuries mean England will be without Manu Tuilagi and Brad Barritt, their centre-pairing in last year's win over New Zealand at Twickenham.
Since winning the World Cup in 2003, England have started 26 players in 39 different combinations.
By contrast, earlier this month the world champion All Blacks fielded Conrad Smith and Ma'a Nonu together for the 51st time, a Test world record for a centre duo.
With just under two years until England host the next World Cup, Lancaster would love to establish a pairing in a key decision-making area of the field.
He certainly has plenty of options with the likes of Billy Twelvetrees, Henry Trinder, Kyle Eastmond, Luther Burrell, Jonathan Joseph and Joel Tomkins all vying for the number 12 and 13 shirts.
Lancaster gave a possible indication of his thinking last week by labelling Northampton's Burrell as the form centre in the Aviva Premiership.
A partnership between Gloucester's Twelvetrees, renowned for his handling skills, and the dynamic Burrell could start against Australia but it would mean Burrell switching from inside centre to outside centre.
Lancaster is also without one of his first choice back-row forwards now that Tom Croft is recovering following knee surgery.
But Lancaster doesn't have a free hand when it comes to naming a replacement.
Exeter's Dave Ewers and Northampton's Sam Dickinson have both impressed at number eight for their respective clubs this season.
However, both players missed out on selection for the original England senior and reserve squads named in August which means that, under the terms of the Rugby Football Union's player-release agreement with the Premiership, it will be difficult for Lancaster to select them now.
"Picking a player from outside the squads is a challenge. It can be achieved, but it's not been achieved yet," Lancaster said last week.
While several players are trying to forge Test careers, the likes of 28-year-old Toby Flood, competing for the fly-half position with Owen Farrell and Freddie Burns, are desperate to show Lancaster they are not surplus to his requirements.
"It's difficult. For me it's about playing well and managing my form at Leicester and then hopefully the decision is made in my favour," Leicester captain Flood, capped 57 times by England, told Sky Sports News on Tuesday.
"It's about getting as much as possible from the next few games.
"There is stiff competition at fly-half but that's also the case for hooker and the back row.
"There's some nice competition building up and the challenge is to get that shirt."