New Wallabies No.8 Ben McCalman says he knew he was made for Test rugby when he put a dent in Springboks giant Pierre Spies with his first touch at the elite level in Brisbane earlier this year.

That was 22-year-old McCalman's Test debut and the Western Force forward will start for the first time in just his third match in Saturday's (0100 Sunday AEST) Tri-Nations clash with South Africa in Bloemfontein.

It caps a meteoric rise for McCalman, who hails from a 6,000 acre wheat and sheep farm near Warren in the NSW central west and who only made his Super 14 debut this year.

But he convinced himself he was ready to play for the Wallabies with that first touch in Australia's Tri-Nations opener in July.

"I didn't expect to get it and then ran into Spies expecting pretty heavy contact but luckily got the better of him on that occasion," McCalman said.

"I just felt, 'How good's this? Give me some more'."

It's that take-no-prisoners approach, inspired by watching Jerry Collins and Toutai Kefu, which first attracted Wallabies coach Robbie Deans to McCalman after watching him play club rugby in 2009.

"We noticed his love of the physical exchanges, he's a bloke who's not daunted by anything," Deans said.

"He's done really well off the bench.

"He'll bring what he's got which is a real physical presence.

"He is a lineout option and he's handled that very well so I guess that's another element that we get."

McCalman's promotion comes after three Wallabies forwards were dropped to the bench and one from the match-day squad altogether following last weekend's 44-31 loss in Pretoria.

Saia Faingaa, Dean Mumm and Richard Brown will all be among the reserves this weekend, while Rob Simmons has been left out of the 22.

McCalman joins hooker Stephen Moore and lock Mark Chisholm, who has been included from outside the match-day squad.

Deans, though, denied anyone was being punished for the meltdown at Loftus Versfeld, when Australia's attacking lineouts failed miserably.

"It's not so much relative to shortcomings," Deans said.

"What we get out of it as well, when you look at the big picture, is we get a lot of mobility and experience coming off the bench so we've just rearranged the order, we haven't really rearranged the playing group."

The Wallabies suffered a scare on Wednesday when star centre Matt Giteau rolled his ankle at training but medical staff say he is in no doubt for Vodacom Park.

Moore, with winger Drew Mitchell, will play is 50th Test, while Chisholm has been handed perhaps a last chance to cement a place in Deans' World Cup plans with James Horwill and Dan Vickerman to return to the side.

"He's got a big frame, we want him to use it," Deans said.

"We're bringing in experience there and that will benefit us at set-piece."

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