Reds playmaker Quade Cooper is bracing himself for a battle of strength against Rebels playmaker James O'Connor in their Super Rugby duel on Friday.

O'Connor has been named as Rebels captain in what will be his 50th Super Rugby cap at Melbourne's AAMI Park.

Cooper normally makes up a Wallabies attacking threesome with the injured Kurtley Beale and James O'Connor but this week they will be against each other.

O'Connor has been playing at fullback so far this season but over the years he has shown he can play anywhere in the backline with success.

Twenty-two-year-old O'Connor has bulked up and now tips the scales at 90kg which is almost 10kg more than when he made his Wallabies debut in 2009.

"He's grown up a lot and he's a lot bigger," Cooper told AAP.

"He's not like a little 18-year-old anymore."

"He's actually now a very powerful player and is a lot bigger than what people's memories of him are when he burst onto the scene.

"He's worked hard at his strength and his power and it's come right into his game with how many tackles he breaks and his defence."

While Cooper himself has bulked and toughened up due to his boxing career he has also worked on his defence after returning from his knee reconstruction last year.

"I've worked really hard at it and I've spent a lot of time in the gym to be strong when I come into contact and it's started to work in my favour," he said.