Wallabies halfback Will Genia says one backward step could spell doom for the NSW Waratahs in their sudden-death Super 14 semi-final against the Stormers in Cape Town on Saturday (0310 Sunday AEST).

Genia, who led the Queensland Reds to a 16-13 round-11 victory over the Springbok-laden South Africans in Brisbane last month, believes the Waratahs have the experience and firepower to storm Newlands and qualify for next weekend's tournament decider.

But only if they play confrontational, in-your-face rugby for the full 80 minutes.

"The Stormers are a very good attacking outfit and, once they get on a roll, they can make those off-loads and they thrive on that continuity," Genia said on Wednesday.

"So defence is a massive thing against these blokes. If you shut them down, take their space and stop them from getting over the advantage line and getting those off-loads away, you stop that continuity.

"That makes them play that sort of grunt game which they haven't played that much this year.

"That goes a long way towards winning the game and that's something we focused on when we played them."

Wallabies coach Robbie Deans believes the Waratahs face an almighty battle conquering the Stormers in front of some 52,000 parochial fans, but suspects the reward for an upset win would be a home final in Sydney.

Deans is convinced his former Crusaders can do a job on the Bulls in the earlier semi-final being played in Soweto, instead of the defending champions' high-veldt fortress in Pretoria.

Deans thinks the Bulls may have lost momentum after resting 14 players in their last-round 38-10 loss to the Stormers.

"The Crusaders, I think, have the advantage of playing away from Loftus and I think it was a mistake by the Bulls to get off the horse, so to speak," he said on Wednesday.

"Anyone who makes it to this part of the competition is capable of pushing on but the Waratahs have probably got the harder part of the equation, to be fair.

"The Stormers are desperate. They've never won a title - nor have the Waratahs - but Newlands, Cape Town, and with the potent mix that the Stormers have in terms of playing the game, they've got all the ingredients.

"So it will be a big effort to achieve, but the Waratahs are capable of it and their timing is good.

"Their mix, not only in terms of personnel, but also the way they're playing the game is coming to a head.

"There's no doubt they can do it. If they do, they will fully warrant it and would probably end up with a final in Sydney, which would be great."

If both NSW and Crusaders win this weekend, the Waratahs would host the title match because they finished the regular season above their trans-Tasman rivals.

Playmaker Berrick Barnes is confident NSW can do their bit to host the final, insisting playing the Stormers in Cape Town holds no fears for the Waratahs.

"Every other team is on holidays and we're getting the opportunity to play footy and there's no better environment than in front of a crowd that's been waiting for their team to be in the semi-finals," he said.

"It's going to be huge."

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