Australia has suffered a massive Rugby World Cup blow after prop Benn Robinson was ruled out for the rest of the year with a knee injury.

The 26-year-old damaged his knee at Wallabies training on Tuesday, with scans on Wednesday revealing he had torn his anterior cruciate ligament.

Robinson will undergo surgery in the coming days, meaning he will miss the upcoming Tri-Nations and the World Cup, kicking off in New Zealand on September 9.

Wallabies coach Robbie Deans conceded the injury was a significant blow to Australia's prospects.

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

"No one likes to see injuries like this.

"The seemingly-innocuous circumstances in which it occurred only adds to the frustration, but injuries have always been a part of the game.

"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."

Robinson had been due to feature in his 43rd Test in Sunday's clash with Samoa in Sydney but his injury may see either Western Force prop Pek Cowan or NSW Waratahs veteran Al Baxter to come into the 22-man squad.

The pair trained with the team on Wednesday, with Deans to decide on a replacement in the coming days.

Robinson's injury also opens the door for Queensland Reds loose-head Ben Daley to challenge starting props Benn Alexander and Sekope Kepu for the Wallabies No.1 jersey in the Tri-Nations.

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