Intense competition for Rugby World Cup spots is helping transform Australia's once-maligned scrum into a key Wallabies attacking weapon.

For years Australia's eight at the set piece was a laughing stock but the burgeoning front row of Ben Alexander, Sekope Kepu and hooker Stephen Moore humiliated Springboks captain John Smit in his Durban swansong at the weekend.

Clinging to a two-point lead as the clock wound down, the Wallabies targeted Smit when he moved from hooker to tighthead and shoved the Boks scrum sideways, earning a crucial penalty that allowed James O'Connor to kick Australia five points clear.

"That was a massive mental edge for us," Kepu said. "That forced them to actually try and score a try."

The Wallabies held firm in the tense closing stages for a 14-9 victory, marking the first time in almost half a century Australia had won successive Test wins in South Africa.

Wallabies forwards rarely get the plaudits, but Alexander said drawing a scrum penalty was as satisfying for a front row as any fancy backline try.

"We felt it was coming and we were slowly getting the ascendancy and just kept working and kept working and finally we started to feel a few cracks (in the Boks scrum)," he said.

"A lot of that was the result we'd done earlier as an eight and eventually we got some pay for it."

While Moore and Tatafu Polota-Nau have been alternating as starting hooker for the past few seasons, Alexander and Kepu began 2011 down Australia's front-row pecking order.

But injuries to Benn Robinson, James Slipper and Ben Daley opened the door and the incumbent trio have gone from strength to strength while starting in all four Wallabies Tests so far this year.

They credit Wallabies scrum coach Patricia Noriega and a huge workload at a Gold Coast training camp last month for the big strides made against the All Blacks and Springboks in the past two Tests.

"We wanted to take a step each week and it started with Samoa," Alexander said.

"As a group, we've been all working really hard with Parto (Noriega) and doing our individual analysis and it's started to come together just through sheer work.

"We did about 40 (scrums) in one day. My back was feeling it.

"But we're nowhere near where we want to be. There were still a couple of scrums (against the Springboks) that weren't up to scratch.

"So until we put in a complete performance we won't be happy."

Wallabies coach Robbie Deans will name his 30-man World Cup squad on Thursday and Kepu said there was simply no time for the front-row hopefuls to rest on their laurels if they wanted to be part of the global tournament.

"With guys like Benn Robinson and James Slipper and Ben Daley back home, you go out there and give it your best and, whatever happens after that, it's in the coach's hands," he said.

"At this level, every week you take it as it comes. It may be the last time you wear the jersey so you go out there and give it your all and try and do your best."

It would be a huge surprise, though, if the incumbent front row wasn't taken to New Zealand next month - especially with Robinson on Monday night ruling himself out of the tournament.

Robinson tweeted that he was "heading in for surgery tomorrow".

"Pushed real hard to make it, but knee just isn't right!! Very disheartening!!" he tweeted.

With Robinson out, Daley is probably fighting reserve Salesi Ma'afu for the fourth and final prop spot.

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