Rennie details what Suliasi Vunivalu has to do to break into Wallabies starting side

Skipper James Slipper says the Wallabies could unleash Suliasi Vunivalu on their northern hemisphere tour, after the code-hopping NRL star missed selection for Australia's six Rugby Championship games.

Both Vunivalu and All Blacks convert Roger Tuivasa-Sheck resemble Ferraris parked in the garage, showing the difficulty in switching from NRL stardom to union regulars.

At least Tuivasa-Sheck will feature in Saturday night's Bledisloe Cup, named on the bench for his first taste of Rugby Championship action.

Vunivalu has spent two seasons with Queensland Reds chasing his Wallabies dream after winning two premierships in five years at Melbourne Storm.

So far, the try machine has five minutes in a Wallabies shirt to his name.

"He's not far away," Wallabies coach Dave Rennie insisted.

Rennie said the Fijian-born 26-year-old faced two challenges: his engine, and the form of players in front of him.

"He needs to convince us at training around high speed and repeat speed," he said.

"He's certainly got some attributes that we know he'd excel at at this level, but it's the whole package.

"When you look at people like, in the backfield, (Andrew) Kellaway and Tom Wright, Marika (Koroibete), they have got a massive work ethic. I'm not sure if everyone appreciates the work those guys do off the ball.

"The decision-making around starting those three is pretty straightforward."

Slipper said the gun recruit was "coming along well" in Wallabies training.

"He's obviously had quite a few injuries, especially through Super Rugby. Not being at his club I wasn't too sure what was going on there with his hamstrings," he said.

"At the moment he's really fit and he's training well.

"He'll feature at some point throughout the year. He just needs to get that time in the saddle, on the training paddock, and then hopefully get some games on later in the year."

Across the Tasman, the struggles of 2018 Dally M winner Tuivasa-Sheck are also raising eyebrows.

The 29-year-old also has just one substitute start to his name since ditching the Warriors for a shot at the All Blacks last year.

He has missed the chance to start at Eden Park, with coach Ian Foster favouring Jordie Barrett to move into midfield with David Havili and Quinn Tupaea injured.

It has prompted some to ponder whether there will be space for Tuivasa-Sheck as the All Blacks gear up for a World Cup, but Foster insisted "he has his chance".

"He's in the All Blacks squad, he's training with us and he's making strides all the time," Foster told Kiwi radio outlet Newstalk ZB.

"It's a matter of trying to give him as many experiences as we can.

"He's played a couple of games for (NPC side) Auckland in the last month. He's a very determined man.

"There's still a bit of growth in him. It's growth that's needed but we're certainly backing his move."