"Our protocol is to talk to the players before we talk to the public."
Barnes, renowned for his reliability, has strong kicking skills more suited for a conservative field-position game while regular fullback Beale is a more explosive, ball-running No.10.
Utility back Barnes' solid performance in his first Test as a fullback in Saturday's 23-19 win over Argentina would've made the decision even tougher.
But Deans insisted his choice was in no way an indication of the style of game he intended to play to continue Australia's recent dominance over the Springboks, winning seven of their past eight contests.
"I don't think it will make a lot of difference either way," he said.
"As you've seen with the way we structure our game, you'll see both players involved in both roles, so it really doesn't matter."
Australia will be looking to save face in their Rugby Championship campaign and can finish second in the series with wins over both the Springboks and the Pumas.
Under-fire coach Deans would also welcome two wins on the road, but asked if it would alleviate any of the pressure on him in the wake of repeated losses to the world No.1 All Blacks he said: "No I doubt it."
"There's always pressure, but I like the way you're thinking.
"(Two losses would be) more of the same. It's all part of it."
Injured trio Sitaleki Timani (hamstring), Stephen Moore (hamstring) and Dom Shipperley (finger) were all passed fit to travel while NSW prop Paddy Ryan and Western Force winger Nick Cummins were the only uncapped players named in the squad.
Wallabies squad: Backs - Berrick Barnes, Dom Shipperley, Adam Ashley-Cooper, Pat McCabe, Digby Ioane, Nick Phipps, Brett Sheehan, Anthony Faingaa, Kurtley Beale, Mike Harris, Ben Tapuai, Nick Cummins.
Forwards - Radike Samo, Michael Hooper, Dave Dennis, Nathan Sharpe (capt), Kane Douglas, Ben Alexander, Tatafu Polota-Nau, Benn Robinson, Stephen Moore, Saia Faingaa, James Slipper, Scott Higginbotham, Liam Gill, Sitaleki Timani, Rob Simmons, Paddy Ryan.
-AAP