Fullback Kurtley Beale has a hamstring injury and is rated "touch and go" to play for Australia in Sunday's World Cup semifinal with New Zealand at Auckland's Eden Park.
Scans have revealed the brilliant attacking back, who left the field five minutes before the end of the Wallabies 11-9 quarterfinal win over defending champions South Africa in Wellington last Sunday, has a "mild hamstring" strain.
However, no decision has yet been made on whether he will play against the All Blacks this weekend.
"It's touch and go and Kurtley hasn't been ruled in or out and our team's medical staff is doing everything they can to get him to the starting line," an Australia team spokesman said on Tuesday.
Beale's absence would be a significant blow for the Wallabies as he adds penetration with his runs from deep and is assured under the high ball.
Teammate Adam Ashley-Cooper said Beale would be a "massive loss" but the team has several replacement options should he not be passed fit to play.
"Hamstrings are funny. They can keep you out for 10 weeks or 10 days, you just don't know. It all depends on how the recovery goes," Ashley-Cooper said.
"He'll be a massive loss for us because Kurtley provides so much to the team, not only in attack but just in the mood and excitement of the group.
"We certainly have our fingers crossed for Kurtley."
Utility back Ashley-Cooper said he would play anywhere that helps the team if Beale fails to make the semifinal between the trans-Tasman rivals.
"I've played my best football where I've actually been changed (positions) that week, so I'll welcome that challenge if it occurs," he said.
Wallaby scrumhalf Will Genia said Australia had the squad strength to cope without Beale.
"It would be a big blow, but you'd have to deal with it. It's not something you can dwell on and worry about," Genia said.
"He's a world-class player, but with the depth that we have in our backline, we'd be able to cope."
Ashley-Cooper, who has played at fullback, in the centres and on the wing for the Wallabies, said he was hoping to get his hands more on the ball against the All Blacks after touching it just once in 80 minutes at outside-centre during the backs-to-the-wall defeat of the Springboks.
"I think I only had one ball carry. I might have touched the ball defensively, in wrapping the ball up, but I'm not sure I had a ball carry," he said.
"It probably doesn't look too good on the stats sheet."
The Wallabies were forced to make 147 tackles to South Africa's 53 and won despite having just 44 percent possession and 24 percent territory in the match.
Ashley-Cooper, recalling his "relief" after the final whistle in Wellington, said: "I don't know if you saw me, but I was on halfway jumping up and down, doing pirouettes, and jumping up and down like a fairy. I was carrying on.
"That might explain the emotion I was going through.
"The whole week I was reflecting on the result back in Marseille (when England defeated Australia in the 2007 quarterfinals) and just what it felt like post-game.
"I tried to share as much as I could with the blokes around me on the feeling they would encounter if we came up short, how unpleasant it is.
"To get the result and go on further than we did four years ago was just pure relief," he added.
Ashley-Cooper said two-times champions Australia had taken huge self-belief out of their gritty win over the Springboks.
"You can take a lot out of it. Knowing we had no possession, we played the majority of the game down in our own 22, they played all the football, they played great football.
"It was just sheer determination and guts that got us the result. We can take a lot of belief out of that."
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