After returning from a brutal tour of South Africa, coach Jake White has turned to 20-year-old monster Oosthuizen for an injection of physicality when he makes his Brumbies debut.

The junior Springbok is the biggest player on the Brumbies' roster, weighing close to 120kg and standing 198 centimetres.

White plucked him from the Currie Cup, where he was playing for the Johannesburg Lions, last year offering him a chance to chase his rugby dreams in Australia.

So far he's had to bide his time on the fringe of the top squad. But White is ready to throw him into the deep end when he takes over in the second row for his first starting cap.

''We're playing a physical team and I pride myself on physicality,'' Oosthuizen said. ''You only get one chance to make a statement and when you get it, you have to make sure you do it right.

''I think my size is just genetics, I started to get big when I was 14 or 15 years old. Before that I was pretty basic, pretty normal. I don't want to prove a point, but I want to show them [South Africa] the choice I made hasn't changed me wanting to make a name for myself.''

Oosthuizen grew up on a South African diet of ''meat, all kinds of meat''. Living with squad prop Ruan Smith, they often host a braai - South African barbecue - for teammates cooking kilograms of steak.

Oosthuizen outsizes Brumbies wrecking ball Fotu Auelua (115kg and 189cm). In fact, the only player at the Brumbies that is the same weight is prop Ben Alexander and while Sam Carter is two centimetres taller, Oosthuizen is 10kg heavier than his fellow second-rower.

He has shed 4kg since arriving in Canberra last year to start training with the Brumbies, and now gets his chance to impress by replacing Carter in the starting side. But he'll have his hands full containing his former junior Springboks teammate and Bulls lock Paul Willemse in the round-seven clash.

Willemse is 127kg and 200cm tall and teamed with Oosthuizen to form a frightful combination for junior South African teams.

Their careers have taken off in different directions and Oosthuizen admits a chance to play for the Wallabies in the future is enticing.

He's preparing for a tirade of abuse in Afrikaans from the players he grew up with when he runs out for the Brumbies.

''I haven't copped too much early on … it doesn't matter where you play as long as you take pride in who you're playing for,'' Oosthuizen said. ''Canberra is the best place for me at the moment, you have to build your future. You can't put your career on hold. I think there will definitely be a few insults from the Bulls, they'll try to get my head out of the game but I'll be able to understand whatever they say in Afrikaans. But I'm not going to retaliate, my job is to be physical … the Bulls try to intimidate you but I'm not going to back off.''

White took Oosthuizen on the Brumbies' two-game tour of South Africa but used the trip to help the developing forward gain an insight into the team.

Oosthuizen was shocked when White told him he would be making his debut against the Bulls and admitted to pre-game jitters.

He already has a rivalry with the Bulls after growing up in Rustenburg and beginning his rugby career in Johannesburg. The Bulls were the team he loved to beat most and it adds extra spice to his first Brumbies appearance.

''[Having played for the Lions] the Bulls are the one team you never want to lose to and you always want to bash,'' Oosthuizen said. ''I was surprised about the call, but I'm ready for it. I feel strong and fast … I'm just looking forward to seeing what I can do now.''