Harry Kewell and top scorer Tim Cahill said they were fit to play, and took part in training after being doubtful for the Group D match with groin and neck strains respectively.
"We're sharp, we're fit, we're strong. Again we are up for this," Kewell told reporters before a late afternoon training session a day before the start of the tournament.
The Socceroos face Germany in Durban on June 13.
Cahill came off at halftime during the team's final warm-up match against the United States after hurting his neck trying to head the ball.
A doctor gave him the okay after the match but he sat out part of Tuesday's practice, raising concern the key player would miss the Germany game.
Kewell remained on the bench for the friendly but is seen fit after recovering from a groin problem suffered playing for Turkish club Galatasaray earlier this year.
"I feel great, we are working hard all the time. The team is looking good ... we are as prepared as we can be," he said, adding it was now up to the coach to decide how big a part he would play.
Kewell said Germany were always tough opponents, and would be on Sunday, despite a spate of injuries.
"Everyone is looking for these angles against the Germans, saying they are a young team, saying the pressure is going to be on them, they are willing to go forward," he said.
"But let's not forget every time they come up to a big tournament they are always the favourites to near enough win it."
Cahill said, as always for Australia, defence would be key.
"I think we have to work off the basis of making sure we don't concede, and then hopefully going on to win the game," he said.
"We have watched a lot of the German team already. I want to make sure that I'm on my game to hopefully make an upset on the day."
Australia, ranked 20th by FIFA and in their third World Cup, also face Ghana on June 19 and Serbia on June 23.
