"There's no gambling here. I have to pick a team to do a certain job on Saturday night and I feel this is the best team to do that," he said.
The pre-match focus has honed in to a degree on Scott Higginbotham -- to some a surprising choice at No8 ahead of Ben McCalman, who had started every match under Cheika's reign but is not even in the squad to face the Springboks.
In the space of a few hours on Thursday, Higginbotham was described as one of the best in the world in his position by former South Africa captain Bob Skinstad and an underachiever who has never played to his potential by World Cup-winning coach Bob Dwyer.
The Melbourne Rebels captain has long been criticised by some as playing too loose and lacking the workrate for a No8 but he finds himself in the Wallabies side because of his leaping ability at lineouts and his mobility, which gives another edge to an Australian side committed to unpredictability in attack.
Higginbotham won Cheika over with his performances at training and the coach said he believed he was ready to disprove his knockers.
"I think Scott Higginbotham has just really impressed me over the past two or three weeks of training in camp, first while Super Rugby was still on, then in Caloundra [Sunshine Coast] and now down here," Cheika said. "He's really put a strong case forward to be selected.
"He's got an opportunity on Saturday night to show what he can do and I'm sure he'll take it."
The Wallabies have lost four of the past five meetings between the sides.
South Africa emerged victorious on their last visit to Suncorp Stadium, but had lost on all seven previous meetings at the ground by an average margin of 20 points.
The Wallabies have just one win from their past seven tests, their worst run of form since 2009.
The Wallabies haven't scored more than two tries in their past eight games against the Springboks, scoring less than two in six of those games.
South Africa's past four victories over the Wallabies have all been by margins of 18 points or more.
Australia v S Africa
Suncorp Stadium, 10.05 tonight
Israel Folau
Adam Ashley-Cooper
Tevita Kuridrani
Matt Giteau
Rob Horne
Quade Cooper
Will Genia
Scott Higginbotham
Michael Hooper
Scott Fardy
Will Skelton
Rob Simmons
Sekope Kepu
Stephen Moore (c)
James Slipper
Tatafu Polota-Nau, Scott Sio, Greg Holmes, James Horwill, David Pocock, Nick Phipps, Matt Toomua, Kurtley Beale.
Willie le Roux
JP Pietersen
Jesse Kriel
Damian de Allende
Bryan Habana
Handre Pollard
Ruan Pienaar
Schalk Burger
Marcell Coetzee
Francois Louw
Victor Matfield (c)
Eben Etzebeth
Jannie du Plessis
Bismarck du Plessis
Tendai Mtawarira
Adriaan Strauss, Heinke van der Merwe, Frans Malherbe, Lood de Jager, Oupa Mohoje, Cobus Reinach, Pat Lambie, Lwazi Mvovo.
- AAP
