The Waratahs have vowed to atone for Saturday night's humiliating 96-19 defeat to the Crusaders when they battle the Brumbies in the semi-finals on the weekend.

Bob Dwyer put his charges through their paces for the first time since the devastating defeat on Monday afternoon, and says he thinks that after his players learned the Reds were out of the semi race and no chance of claiming NSW's second placing, they may have relaxed.

"I've tried to think it through a bit," said Dwyer. "The only negative I can see is that about five minutes before we were due to run on the field we got the news that Queensland had been beaten and so second spot was assured.

"Whether that had a subconscious effect on the team I don't know, but going into the game we had a good frame of mind and the captain's run was extremely good and the pre-match build up was good.

"I think the main thing responsible for it was the performance by the Crusaders and our lack of mental toughness and maturity in being able to focus properly on how to stop the situation."

Waratahs halfback Chris Whitaker agreed that the news from Dunedin about Queensland may have affected his team's performance: "It might have, but there's definitely no excuses, if anything getting a home semi-final should pump you up a bit to have a good game," Whitaker said.

Whitaker and winger Scott Staniforth agreed that the team still believes in itself, and both are confident they can win the tournament, but only if they can vastly improve on Saturday night's efforts.

"Maybe we have been a little more tentative, more worried about the results than how we're playing, definitely this week we've got to worry a bit more about how we're going to play," Whitaker said.

"Because you only get one chance at it now, it's do or die, you lose and you're out. We've just got to show a bit of ticker and go out there and play football and not worry about the result."

"We've all got to step up," Staniforth said. "On the weekend, we went into our shells and look what happened. We've got to come out and lead from the front."

Dwyer also defended his decision to make changes to the starting line-up, saying that with Phil Waugh, Marc Stcherbina, Nathan Grey and Rod Moore all injured and either out of the game or heavily restricted, there wasn't much more he could have done.

The coach believes his team will go into the game as an outsider after the Brumbies' improvement of the last two weeks, but is also confident that a return to its home turf will hold the team in good stead.

Dwyer will name his squad for the match later in the week, but hasn't ruled out a possible switch of skipper Matt Burke from outside to inside centre and the inclusion of Luke Inman in the place of Sam Harris.

Meanwhile Brumbies flanker George Smith says he and his teammates are reading nothing into the massive loss by the Waratahs, saying it will mean nothing when Saturday's match begins.

"I guess it's a confidence blow to lose by that much, but we're sure they'll put it behind them and come out this week firing," he told AAP. "They're a classy side. They've showed that all year. They've just had a mishap in one game."

Outside centre Stirling Mortlock is another wary of New South Wales after the thrashing, saying that if anything he expects the Waratahs to come out breathing fire in an attempt to make up for it.

"The semis are a completely different ball game," he said. "They'll be full-on and I'm sure that was just a one-in-ten-years game."

On a personal note, Mortlock expects to take his place in the Brumbies team despite struggling with an ankle injury that forced him from the field in Friday night's 46-25 win over the Blues.

"I've already had two days off and its going pretty well," he said. "It was more precautionary me coming off, because it just wasn't 100 per cent right."

Fly-half Stephen Larkham also dismissed suggestions that the ACT will attempt to use the same attack at all costs approach to the game that paid such handsome dividends for the Crusaders.

"Certainly a lot of the stuff Canterbury did were very risky options," he said. "They came off on the day, but as a general rule you wouldn't like to use that mentality going into a game of this proportion."

Larkham refuted the idea that his team has an advantage when it comes to big matches: "I think a lot of those NSW players have played for Australia and they have played in big matches before," he said.

While the Brumbies struggled to four losses in a row in the second half of the season, captain George Gregan says his team knows what it must do to step up when the semi-finals begin.

"It's the type of football we like to play," Gregan said, before adding that he expects the Waratahs to find it hard to recover from their loss. "I think when you get beaten by that margin it's going to have some psychological scars, that's for sure.

"Whether or not they'll be able to turn it around in seven days, well see, but it's certainly going to be in the back of their minds and it's not a good way to go into the semi-finals, that's for sure."