Former NRL winger Cooper Vuna is being groomed as an inside centre for the Melbourne Rebels' debut Super Rugby season.

The ex-Newcastle Knights try-scorer played almost exclusively on the wing in his seven-year league career, but is favourite to start at no.12 for the fledgling Rebels' franchise.

The 23-year-old's prospective centre partner and captain, Stirling Mortlock said Vuna will play in the midfield if he can get his head around the rule differences in the 15-man code.

"The hope is if we can get the best out of him and keep on working on that rugby knowledge and that rugby skill, he could be a really good centre," Mortlock said.

"So far the signs have been really pleasing with Coop. He's got a lot to learn in the game and particularly if he plays in the centres where there's a lot more going on for him.

"The past two games he's played wing, but predominantly inside centre for at least a half both times. So far every match he's improved and he's doing his work off the pitch."

Weighing in at 101kg, Vuna was the second highest try-scorer at the Knights last year.

The Auckland-born speedster played rugby until he was 15 and Mortlock is adamant Vuna can be their best kept attacking secret if he adapts back to union quickly.

"He's got a bit of X-factor in his running game. He sometimes does things that you just don't expect him to do and he's a pretty good one-on-one defender as well," said Mortlock.

"He's a really thick-set bloke, very dynamic, and if he's really diligent and we work hard together, it could be a really potent area for him."

The Rebels also have high hopes for their other NRL recruit Jarrod Saffy.

In line to play blindside flanker, South African-born Saffy will also draw on his experience playing rugby as a junior.

Making the code switch as a forward is generally accepted to be a tougher challenge, but the Rebels are hoping Saffy's grounding in the sport means he can make a smooth transition. Just like All Blacks star Brad Thorn was able to do years ago when he switched to the Crusaders from the Brisbane Broncos.

"That's definitely the hope and in the trials it looks as though he's certainly played rugby for a while, not a guy who has just won a premiership in league," said Mortlock.

"Jarrod's got the benefit of playing rugby for a fair while, so for him it was always a timing thing."

Inaugural coach Rod MacQueen said combinations are the biggest hurdle he has to overcome leading into the club's first match against the Waratahs in Melbourne.

MacQueen is excited about having Vuna and Saffy on his list, as well as Luke Rooney, who also played many years in the NRL before switching to European rugby.

"Every sport brings something else to another sport, so I'm sure rugby league can offer us some things that Sonny Bill Williams does for the All Blacks. That helps, there's no doubt," he said.

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