Socceroos in defensive reshuffle at cup

The Socceroos have been forced into a defensive reshuffle with Fran Karacic replacing an injured Nathaniel Atkinson for the crunch World Cup game against Tunisia.

Right-back Atkinson has failed to recover from an ankle injury suffered in Australia's 4-1 loss to France in their opener in Qatar.

The 23-year-old was troubled by an ankle ailment prior to arriving in Doha.

"He got a bit of a knock on the ankle again," Australia's coach Graham Arnold told reporters ahead of Saturday's match.

"Fran Karacic will come in, we have got him ready for the game."

The Australians must win or draw against Tunisia at Al Janoub Stadium on Saturday to retain a chance of advancing from a World Cup group for the just the second time.

The Socceroos are also likely to summon influential midfielder Ajdin Hrustic, who missed the opening game and hasn't played since copping an ankle injury in Italian club ranks on October 3.

Coach Arnold rates Hrustic 95 per cent fit but, beyond Karacic's inclusion, was reluctant to detail any other changes.

"He (Hrustic) trained well, he's recovering well, he's mentally and physically in good shape," Arnold said.

"I don't think there will be too many changes, we have got to put our strongest line-up out.

"It will be very, very physical game. The Tunisians like a physical game and we have got to match that physical aspect."

Hrustic shapes as a potential replacement for Riley McGree in a fixture kicking off at 2100 AEDT, a prime time slot in Australia.

Socceroos defender Aziz Behich said the squad was boosted after their France failure by footage from Melbourne's Federation Square of jubilant supporters celebrating Craig Goodwin's goal.

"We all saw the footage after Goody scored and it gives us goosebumps that you do that to the nation back home," Behich told reporters.

"It (the Tunisia game) is a perfect time for everyone back home.

"We're going to go out there all guns blazing.

"And when that final whistle goes, we want to see more footage of everyone at Fed Square going crazy again.

"We know what is ahead of us ... it's going to be a fight and we have got to match that fight and then play our football.

"And that football we played against France in the first 30 (minutes), that has got to be 70, 80, 90 minutes."

The Tunisians, who drew their opener against Denmark and are ranked 30th in the world, eight spots higher than Australia, have never progressed from the group in five previous cup campaigns.

This will be their first meeting at a World Cup - the past two encounters were an Australian 3-0 win in a 1997 friendly in Tunis, and a 2-0 loss at the 2005 Confederations Cup game in Germany.