Wallabies coach Michael Cheika earmarked Faingaa as Australian rugby's in-form hooker on the road to the World Cup but fired what was perhaps designed to be a wake-up call at the 23-year-old.

Cheika said Faingaa needs to get fitter and shed kilograms to capitalise on his footballing ability and build on the six international caps he earned last season.

But McKellar says there must be patience when it comes to a rising star the club plucked off a construction site in the sweltering Sydney heat.

It comes as Faingaa prepares to make his return for the Brumbies in a crucial showdown against the Johannesburg Lions at Canberra Stadium on Saturday.

"You've got to understand Folau is 18 months into a professional career," McKellar said.

"Training time, you need training time and training history to build your fitness over a period of time. You don't just go from a worksite and within 18 months become an elite athlete.

"It takes time, education, and him learning to make good choices away from training. Folau is a tremendous kid and a great footballer, he will continue to get fit by just being in a professional program. We're not just going to flick a switch.

"He's a big man, that's a positive for him."

Faingaa will lock horns with a Lions skipper in Malcolm Marx desperately looking to fire during a three-week stint in Australasia.

Marx has endured an inconsistent campaign and will need to rediscover the form that saw him emerge as one of world rugby's most revered players if the Lions are to claw their way to the top of the South African conference.

If anyone is up to the challenge of going toe-to-toe with a Springboks star on a mission, Brumbies captain Christian Lealiifano says it is Faingaa.

As determined as Marx is to find form to kickstart a winning run, Faingaa must be equally desperate with the Brumbies' season hanging by a thread.

The Brumbies have won just two from seven this season and need to start racking up wins if they are to have any chance of featuring in the finals.

"All along Folau has been the kind of guy that is not too phased by a lot. He is really relaxed, you always see him smiling," Lealiifano said.

"He is not really phased by who he is playing, whether they are the world's best player or a debutant. He just worries about himself and his game, and trying to play the best he can, which I love, I love that about him.

"He has got a real edge about him, he doesn't care who he is playing against, which is really nice. It's a real nice challenge for him.

"That'll set the tone for us, the boys up-front in the engine room, so hopefully they can do their job and we'll do ours."

SUPER RUGBY ROUND NINE

Saturday: ACT Brumbies v Johannesburg Lions at Canberra Stadium. Tickets available from Ticketek.