Australia's front-row plans for the Rugby World Cup have stumbled at the first hurdle with the Wallabies' best prop Benn Robinson ruled out for the rest of the year with a knee injury.

Robinson damaged his knee at training on Tuesday, with scans on Wednesday revealing he had torn his anterior cruciate ligament and will miss the Tri-Nations and World Cup, which starts in New Zealand on September 9.

Robinson, one of Australia's most consistent performers in an area that has not been their strength over the past few years, will undergo surgery in coming days.

The 26-year-old's absence has given coach Robbie Deans plenty to think about ahead of Sunday's season-opening Test against Samoa in Sydney.

Waratahs' team-mate Sekope Kepu will take his place in the starting side against Samoa, with Ben Daley (shoulder), James Slipper (ankle) and Salesi Ma'afu (arm fracture) all unavailable.

Ma'afu has resumed training but is unable to complete contact work, Daley is expected to be fit after Sunday week's Tri-Nations opener against South Africa, while Slipper is in a moonboot but expected to return before the World Cup.

Daley could challenge Kepu and Ben Alexander for Australia's No.1 jersey in the Tri-Nations.

Deans admits the loss of Robinson is significant but is confident of the side's depth.

"Robbo's obviously been part of the group for a while, so you don't like losing blokes who have been in the nucleus," he said.

"It's disappointing news for Benn, disappointing news for the rest of the squad and for Australian rugby as a whole.

"When the door closes for one player, it opens for another and I'm sure the other front rowers we have will step up to fill the void Benn leaves."

Wallabies' captain Rocky Elsom also backs his side to deal with the major setback.

"Obviously, he's been a fantastic player for us. You'd love to have all hands on deck but it's like any Test week. If you lose guys, you've just got to fill it as best as you can - and we've got some good guys to fill it with," Elsom said.

The long-term solution to Robinson's absence and the makeup of Deans' preferred front-row at the World Cup are unknown but the short-term answer could be Australia's most capped Test prop Al Baxter.

Baxter and Pek Cowan were rushed into camp on Wednesday after missing out on the 40-man squad. They both trained with the team and Deans will decide later in the week who claims a spot on the bench for the Test against Samoa.

The 34-year-old Baxter's last Test was in 2009 and he announced last month this would be his last year of rugby union.

Deans notes Robinson's shock injury is the perfect example of why he won't engage in crystal ball gazing before selecting his 30-man World Cup squad on August 18.

"Obviously, it wouldn't have been our choice, but these things happen. It won't be the last (injury)," Deans said.

"That (naming the World Cup squad) is five Tests away. We'll go Test match to Test match, looking to maximise each outing, and then we'll contemplate selection of that squad.

"You can't take anything for granted - look at Robbo's situation. There's no point looking beyond now."

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