Former Test skipper Tony Shaw has demanded the Wallabies develop a killer instinct and end the Tri-Nations with a flourish to be genuine World Cup contenders.

Shaw bemoaned the inconsistency and inability of Robbie Deans' team to close out winnable Tests, factors he felt had worn out the patience of the Australian rugby fraternity.

The Wallabies great, renowned as one of the hardest men to play the game in his 36-Test career from 1973-82, said beating South Africa and New Zealand in the next nine days was crucial to being in the hunt for next year's World Cup.

"If we're ever a chance of winning the World Cup we have to beat the All Blacks," Shaw told AAP.

"We have to beat them once and if we beat them twice we'll be even more confident.

"We have got to have one good win against the All Blacks and I think for these guys to come out of Africa with some pride they've got to win the next Test (this weekend against the Springboks).

"We can't afford to wait for next season and say `World Cup next year and we'll do well'.

"We have to set the platform now for next year - it's really crucial.

"We are right at the end of the tether. I think we are right at the end of the acceptance period."

More than just the Mandela Plate goes on the line in Bloemfontein on Sunday morning (AEST), with a win also ensuring the Wallabies would avoid the Tri-Nations wooden-spoon.

Shaw said it would also importantly lift confidence for upcoming clashes against the high-flying All Blacks, on September 11 in Sydney and October 30 in Hong Kong.

Between then and the World Cup is a four-Test Spring Tour in Europe and just four more Tests in a shortened 2011 Tri-Nations.

The Queensland Rugby Union president, Shaw is adamant the Wallabies are good enough to regularly beat the top two teams in the world but needed to believe it.

"I think it's about mental strength," said the former back-rower. "It's the strong heads that win games.

"They don't close sides out and they don't finish them off when they have a lead and opportunities and that's the disappointing fact."

"You need players of all the same mindset and that's the same single-mindedness and purpose the Blacks have and Boks - when they put their minds to it - that they can't be beaten, and I don't sense that with the Wallabies.

"I don't think we have that killer (instinct).

"It's coming and I don't want to be critical but that's one thing they need to get if they are to win the World Cup and be a world-class team."

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