New Zealand's selectors, desperate for success against South Africa on Saturday, may switch lock Troy Flavell to blindside flanker for the Tri Nations Test.

But they have resisted the temptation to recall Christian Cullen after just one game since knee surgery in May.

The All Blacks, who crashed 23-15 to Australia two weeks ago, need to complete a double over the Springboks to revive their Tri Nations campaign which started with a convincing 12-3 win in Cape Town.

Australia leads the competition with seven points from three games, South Africa is a point behind and New Zealand has four but has a game in hand.

All Blacks coach Wayne Smith and his assistant Tony Gilbert have previously brushed aside suggestions that Flavell's best position is at No.6.

But they appear to have changed their minds after giving him an extensive run-out at blindside flanker in Tuesday's training session.

Byron Kelleher and Andrew Mehrtens, replacements in the last Test, were also given significant periods as the halfback pairing while Leon MacDonald was back at fullback, with Jeff Wilson moving to right wing.

Cullen scored two tries for Wellington in their 35-17 national championship first division win over Taranaki last Friday, in his first major outing since knee surgery in May.

All Black coach Wayne Smith said Cullen would be given all the time he needed before being pitched into the Test arena, however Cullen may be recalled for the Sept 1 Sydney match against Australia if he comes through another club match successfully.

The Springboks are likely to make one change following their 14-14 draw against the Wallabies in Perth last Saturday.

Centre and vice-captain Robbie Fleck has an ankle injury.

South Africa coach Harry Viljoen has given Fleck only a 20 per cent chance of playing on Saturday.

"It's a big blow to us because he's also our playmaker. I would say Deon Kayser or Andre Snyman will take his place at this stage," Viljoen said.

Springbok goal-kicker Braam van Straaten has called on the Tri Nations administrators to use one brand of ball in the competition.

He said the Gilbert brand used by South Africa was the best of the lot and New Zealand's adidas and Australia's Summit balls should be given the boot.

"The other balls are not evenly balanced and don't travel as far or as straight," van Straaten said today.

He said he was having difficulties with the adidas ball because it was "unbalanced" and its flight not true.

He said the seams and an extra piece of rubber used inside the adidas ball made it lopsided, and its flight in goalkicks and off the hands was deceptive and shorter than the Gilbert ball.

Saturday's Test will be played with an adidas ball while the Springboks used a Summit ball in Perth where both Van Straaten and Wallaby goalkicker Matt Burke succeeded with only 50 percent of their kicks. (AAP)