The star quality of the Wallabies' openside flankers Michael Hooper and David Pocock is undeniable and has forced coach Michael Cheika's hand in starting them both against Fiji. Australia will roll out the brilliant back-row, including rugged blindside flanker Scott Fardy, with Pocock filling the No.8 jersey, in their World Cup opener in Cardiff on Wednesday.

It is just the second time the pair will have started a match together, following a successful outing in a 27-19 win over the All Blacks in Sydney in August, but Cheika admits the combination cannot be held back any longer.

"I just think both of them over the course of the season, and with what they've done in Test footy, it's relatively impossible to leave one out," Cheika said.

While vice-captain Hooper remains in the famous No.7 jersey, the ball-hunting Pocock slots in at the back of the scrum - which he insists will not alter the way he plays the game by any measure. The 27-year-old has trained at No.8 regularly since the end of the Rugby Championship, won by the Wallabies, and has drawn on the experiences of Cheika, a former No.8, and champion five-eighth Stephen Larkham, the Brumbies coach and Wallabies backline coach. It has all given Cheika the confidence to unleash the pair on Fiji.

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"For [Pocock] it's mainly about the scrum control - he's had a bit of a handle on that already," Cheika added. "I believe in him a lot there. He's been very versatile at what he's done."

Cheika stressed it was a great opportunity for the duo, who now get the chance to lock down the spots for the remainder of the tournament.

"I think they've really enjoyed working together," he said. "They've been fierce opponents, obviously. And now there's an opportunity that they probably didn't think they'd ever get, to work together, which they've enjoyed."

Meanwhile, Will Genia has been given the nod at half-back ahead of Nick Phipps, with Bernard Foley edging out Quade Cooper for the No.10 jersey. As expected, veteran Matt Giteau and power-runner Tevita Kuridrani occupy the centre spots, with Israel Folau tipped to star from fullback, while Adam Ashley-Cooper and Rob Horne are on the wings.

In the front row, rising Brumbies star Scott Sio will pack down alongside skipper Stephen Moore and Sekope Kepu, with James Slipper benched after leading the Wallabies in their final warm-up match against the USA. Kane Douglas and Rob Simmons will start in the second-row, with Will Skelton preferred as a powerhouse option off the bench.

"Skelton has done an absolutely outstanding job," Cheika said. "Really, for his age, the way he's come through the system and what he's been able to bring to international football at such a young age in his position has been excellent. It's his first World Cup, so I want him to just earn his way into (the team) and learn a bit more about what the tournament is going to bring - all those little bits and pieces."

Like Phipps and Slipper, Skelton will get some game time against Fiji before earning a start against Uruguay in Birmingham.

Wallabies team to play Fiji:

Israel Folau, Rob Horne, Tevita Kuridrani, Matt Giteau, Adam Ashley-Cooper, Bernard Foley, Will Genia; David Pocock, Michael Hooper, Scott Fardy, Rob Simmons, Kane Douglas, Sekope Kepu, Stephen Moore, Scott Sio.

Reserves: James Slipper, Greg Holmes, Tatafu Polota-Nau, Will Skelton, Dean Mumm, Nick Phipps, Matt Toomua, Kurtley Beale.