It's the individual battle that could register on the richter scale on Saturday night, when man mountains James Horwill and Brad Thorn collide in the must-win Wallabies-All Blacks Tri Nations Test.

Seismologists need look no further than ANZ Stadium for an epicentre should their instruments register a reading as the two aggressive No.4s face off in each team's most crucial match.

Horwill, 24, the 200cm, 115kg enforcer who became a Wallabies regular in 2008, is probably still best known for a photo of his bulging eye after a fierce brawl in the Brisbane match against France last year.

Thorn's hardman qualities are well known on this side of the Tasman following the 195cm, 113kg lock's time with NRL club Brisbane.

There may be 10 years difference in age, but the two aggressors have plenty in common, most significantly both needing to declare last year that their brain-snap days were over.

Wallabies coach Robbie Deans decided Horwill would be part of his plans the first time he saw him play, but the big Queenslander credited his rise to become Australia's No.1 lock, as Dan Vickerman's career wound down, to his on-field anger management.

Thorn, 34, decided enough was enough after a spate of disciplinary problems - sin-binned in the Super 14 final for punching Vickerman, suspended during the Tri Nations for a late tackle on John Smit and yellow-carded again for a high shot on Matt Giteau.

"You certainly know when he hits you," Horwill said of his opposite number on Wednesday.

"You certainly know that he's out there, especially when he gives you one.

"(He doesn't mind a scrap), which is always good, I think most second-rowers like that."

As they prepared to meet head-on in a game which could decide the destination of the Bledisloe Cup in 2009, Horwill said he admired his adversary.

"It's very impressive, isn't it? He just seems to be getting better," he told reporters.

"He seems like the guy that never ages, he seems to stay the same age and perform at the same level week-in, week-out and year after year.

"He's an extremely impressive athlete and someone you've got to admire."

Horwill, who lasted only a half of Australia's loss to South Africa in Cape Town because of a stomach bug, also dispelled any suggestion Thorn was a liability in the All Blacks lineout.

"His lineout has improved over the years," he said.

"It was probably a bit harder to him coming from league where he didn't do too much lineout jumping but I think he's very good.

"At the front of the lineout (he) has the ability to win good ball for the All Blacks and also get them out of tough situations if the pressure's on, he's done that a couple of times against the Springboks."

Meanwhile, Horwill said returning flanker Rocky Elsom was fitting in well as the Wallabies work on their own lineout, which crumbled at the hands of the Springboks.

"We haven't changed anything specifically for Rocky, he's just going to fit into our set-ups," Horwill said.

"He's obviously a very good lineout jumper so that's always a handy person to have."

Wallabies assistant Richard Graham said the coaching staff expected Elsom to last the full 80 minutes despite not having played for nearly three months.

Brought to you by AAP © 2024 AAP