Australia's star rugby union convert Israel Folau has backed Sam Burgess as "a great athlete" who can flourish in the 15-a-side code.

Burgess was a controversial selection for England's World Cup squad, being picked by head coach Stuart Lancaster less than a year after switching from rugby league, where he enjoyed a success-laden career highlighted by guiding South Sydney Rabbitohs to the Australian NRL title 12 months ago.

The Yorkshireman, though, failed to cut it in England's midfield, and he has received considerable criticism since the host nation crashed out of World Cup contention last Saturday through a 33-13 defeat against Australia.

Wallabies full-back Folau played for Melbourne Storm and Brisbane Broncos, winning eight Australia league caps, before forging a stunningly-successful union career. 

Sam Burgess © Getty Images

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"It [converting to union] was pretty challenging in my first year of playing Super Rugby, but I feel like I managed to pick up the game," Folau said. "In terms of Sam, I think he's a brilliant player and his progress, from my point of view, has been going good.

"I don't listen to any other comments from the outside. I just think Sam is a great athlete who can do really well in the union game, I hope he does. I wish him all the best going forward and going into the future."

Wallabies head coach Michael Cheika, meanwhile, is braced for a punishing encounter with Wales after both teams booked last-eight places from Pool A, with England left trailing in their wake.

Cheika said: "We are still right in the middle of what is pretty much a war zone, our group. The goal has been to keep trying to win to get out of our pool, and then go on and keep doing it from there.

"Saturday will, I feel, be the most brutal game we are going to encounter in the pool. It has been physical so far, but my knowledge of tournament play tells me that the further on it goes, the more brutal it gets because the stakes get higher and everyone wants to win more."