Springbok captain Victor Matfield, the most revered line-out jumper in the world, rates the Wallaby line-out as the biggest threat to South Africa's chances of the rare feat of back-to-back victories on the road in the Tri-Nations.

The Boks face the Aussies in Perth on Saturday in their third match of the tournament — having gone one-one against the All Blacks in the first two weeks, losing (8-19) in Wellington and winning (30-28) in Dunedin.

Now they hope to record only their second back-to-back wins in Australasia — following the 1998 victories in Wellington and Perth — which will set South Africa up nicely in the tournament with three home matches to come.

However, despite South Africa and Matfield's reputation as the world leaders in line-out play, the Bok captain — standing in for the injured John Smit — fears the Wallabies may have a few aces up their sleeves on Saturday.

"The Wallaby line-out is always a big threat and they will be very competitive in that department," Matfield said as the Boks stepped up their preparations for the Perth showdown.

"Their different tactical approach provides us with an interesting challenge and they have the advantage of playing at home in their first Tri-Nations match, while it will be our third consecutive away match," he added.

Matfield also dismissed the notion that the Wallaby scrum, so often regarded as the team's soft underbelly, will give the Boks an advantage on Saturday.

Despite the Boks dominating in the line-outs and at scrum time in their win against the Kiwis last week, the rangy Bok lock feels his team will need to step it up another gear this week.

"The public perceives the Australian scrum as weak, but it would be stupid for us to think that. We have been troubled by them in the past and we could get surprised by them again," Matfield said.

"It's all about focus, as in defence. It depends on whether you really want to defend or scrum on that day. We have to make sure we're 100 percent focused in the scrums and we go in with aggression."

365