But the enigmatic playmaker simply wants to make the most of his late World Cup inclusion, vowing to take his opportunity and show his worth at Twickenham.

Cooper got a tap on the shoulder at Wallabies training on Friday to tell him he was a surprise injury replacement on the bench for the quarter-final clash against Scotland on Sunday (Monday morning AEDT).

If he gets on the field, it will be his 59th Test and will put him one shy of the mark set by the ARU that allows players to still be available for Wallabies duties even if they sign overseas contracts.

Cooper's future is yet to be locked in after he reportedly agreeed to a deal in France with Toulon. He wants to play for the Australian sevens side at the Olympics next year.

Two more Test caps would allow him to play in France and be picked in Wallabies squads under the new eligibility rules that have revived centurion Matt Giteau and Drew Mitchell's international careers.

The ARU changed its Wallabies eligibility rules this year to allow players with 60 caps and seven years of service under their belt to play abroad and still be available for Test matches.

But Cooper just wants his opportunity to step up in Israel Folau's absence, and attack coach Stephen Larkham said the linchpin is ready to dispel the myth he struggles in defence.

"This is probably the latest [I've been called up]. We spoke about it as a squad, preparing like you are going to play," Cooper said. "Even watching from the sidelines, I have been going through the game calling, even when I have been sitting in the stands as if I was out there. Just to make sure I was ready if anything happened."

Cooper has played just one game at the World Cup so far, showing his attacking brilliance in an 11-try rout against Uruguay.

But Bernard Foley's form at five-eighth has kept Cooper out of the No.10 jersey and forced him to sit in the stands for the pool stages.

Folau aggravated an ankle injury at training on Friday, forcing him to withdraw from the quarter-final with Kurtley Beale stepping up as fullback and Cooper being added to the bench.

Cooper has been sent to the sin bin in three of his past four Tests, but Larkham said the Wallabies would not tell him to tone down his defensive aggression.

Throughout his career Cooper has been tagged as the defensive weak link in any team he plays for, but Larkham said the 27-year-old playmaker was ready to prove his doubters wrong with a cameo from the bench.

"You don't really want to change him," Larkham said when asked if he would speak to Cooper about his yellow-card run. "I think his attitude is pretty good in attack, and defensively, you don't want to change his attitude there.

"He's been nice and aggressive and been making the tackles he needs to make.

"He's been shifted around in different positions [in defence] at this level and Super Rugby. Some people say he's sort of hidden, but he's a very good defender, a very good tackler and loves to throw himself into that sort of stuff.

"It's just the perception because the coaches decided to put him [in different positions]."

Cooper will offer cover for fullback and five-eighth if he is required from the bench.

The final-eight clash against Scotland will give Cooper a chance to play against cousin Sean Maitland and renew their big-match family rivalry.

"If I get the opportunity I will step in there and bring what I have to the game," Cooper said.

"Every game is a big game, from the moment we got over here it has been knockout football. I am not looking at it as if the quarter-final is the game you want to play.

"Whether you get picked or not, everyone has a role to play and that's something we have been driving at this tournament."