Trim and taut Wallabies fullback Kurtley Beale has declared himself in the best shape of his burgeoning career after shedding up to seven kilograms since the end of the Super 14.

Beale, who has had a history of ballooning during the NSW Waratahs' off-season, says a rigid conditioning program with the Wallabies helped him to his best Test-match performance in last month's 20-10 loss to the All Blacks in Christchurch.

The 21-year-old will again be named at fullback for Australia's Tri-Nations clash with South Africa in Pretoria on Saturday (0100 Sunday AEST).

"I had a lot of excess baggage around the torso here, around the guts," Beale told reporters at Australia's Cape Town base.

"(I lost) about six or seven kilos ... since the end of the Super 14.

"I've been putting a lot of work in, I guess I've had to do this to be a Wallaby.

"You're playing against elite athletes these days and, for me now to be physically at my best ... I feel a hundred per cent better, I'm just a new man I guess."

Beale looked to come of age in Christchurch, where he sprinted 65m to score Australia's only try, a feat he said he would not have been able to manage before his tough fitness regime.

"I've never run that far in my life," he said.

"It's just amazing, if you stick to a plan the results definitely come."

Wallabies assistant coach Richard Graham said Beale's newfound self-discipline was the difference.

"There's a program put in place to help him but he needs to actually show us some support ... it's a credit to him he's done that," Graham said.

"He's a bloke who absolutely backs himself 100 per cent and (head coach) Robbie (Deans) has given him a lot of confidence to do that, supports him to make good decisions on the field and I think we're seeing the benefits of that now."

The entire Wallabies squad are backing their fitness for the Loftus Versfeld clash at altitude after the Springboks appeared to fade in last weekend's 29-22 loss to New Zealand in Soweto.

"Physically, we're ready, we've done the hard yards throughout the last few months ... we're getting good results back from the GPS that we wear," Beale said.

"At altitude, none of the boys get too carried away. You don't want to let it get stuck in your mind because it's not an important factor that we need to focus on.

"We know how to play to beat the Boks and maybe there might be a small factor with being over here.

"But if we go in with the right attitude and the right mindset of what we did in Brisbane (a 30-13 win last month), we're going to give these guys a good run for their money."

The Wallabies haven't beaten the Springboks on the high veldt since 1963.

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