Auckland - Flank David Pocock gave Australia a scare by missing training on Friday on the eve of what could be a tournament-defining Rugby World Cup match against Ireland at Eden Park.
The highly-rated 23-year-old, the only specialist openside in the Australia squad, experienced some tightness in his back and missed the morning training session as a precaution, team officials said.
"He was just a little bit tight so we didn't want to push him," captain James Horwill told reporters. "I imagine he'll be okay, that's the belief that I've got."
Pocock would be a big loss to the Australians for a match where Ireland's mobile back row and experienced backline present a threat to Australia's hopes of dictating their own passage through the draw.
The winner of the match will almost certainly top Pool C, which also includes Italy, Russia and the United States, setting up a quarter-final with the second-placed team from Pool D, likely to be Wales, Fiji or Samoa.
The Eden Park losers are likely to finish second and play defending champions South Africa in the quarter-finals. If they get through that the All Blacks could be waiting in the last four.
"It's going to test us," said coach Robbie Deans, whose team beat Italy 32-6 in their opening encounter.
"We know that this weekend will be another step up from round one, we saw some good rugby in round one but we also saw a little bit of anxiety from teams.
"This match is key for us as it is for Ireland."
Australia came to New Zealand on the back of victories over South Africa (twice) and the All Blacks to win the Tri-Nations, while the Irish lost all four of their warm-up games.
The Irish did give a reminder of what their golden generation can achieve when they hammered England to prevent their rivals from winning a grand slam earlier this year.
Horwill said in any case he did not think form would mean much in what he anticipated would be "one hell of a contest".
"I think they're going to be at their best tomorrow(Saturday), so we have to be at our best to match them," said Horwill.
"They always lift another level every time I've played them, we're expecting that, and we're looking forward to meeting the challenge."
The Australians have been talking up the ball-carrying skills of the Irish back row and the unique threat Irish skipper Brian O'Driscoll, who has scored a number of memorable tries against the Wallabies, presents in the centres.
"We've looked closely at the Irish side and key players and he's obviously a key player for them and we'll be trying to limit those moments this weekend," said Deans.
"He's a class act, been around a long time and played some great rugby. The boys have got a lot of respect for him."
Australia, who have beaten Ireland in all four of their World Cup meetings, have not won a test at Eden Park since 1986 but Rocky Elsom thought that particular hoodoo had limited relevance given the opposition.
"I think Ireland have no better record than us at Eden Park over the last 20 years," said the former Wallabies captain and Leinster flanker. "One of us have got to win."