But the Bosnian insists revenge for their humiliating World Cup defeat to the Socceroos is not an issue, a sentiment echoed by Australian counterpart Graham Arnold who contends much has changed since last year in Kaiserslautern.

"I consider it the toughest match I have faced as Japan coach and consider Australia, from the objective viewpoint I have about this Asian Cup, the toughest opponents we could possibly meet," said Osim.

"As Brazil won the Copa America title after losing their opening game, Australia may possibly do the same.

"They are on course to get better as a whole and formidable as the opponents. On the other hand, we have not yet experienced a poorly played game."

Australia beat Japan 3-1 in their World Cup opener in Germany with all their goals coming in the last eight minutes. The Asian champions never recovered and crashed out at the group stage.

But Osim insists no-one is dwelling on the past.

"It is shocking if you still feel the shock after one year," he said.

"The better team won that match. Japan lacked the right information on Australia. If they are favourites here this year, it means they were not an easy side to beat last year."

Arnold, facing the boot after the tournament regardless of what happens on Saturday, concurred.

"It's a totally different competition with different players and different coaches," he said.

"It will obviously be a very difficult game as Japan have shown form."

Arnold is facing a dilemma over whether to leave Tim Cahill, Harry Kewell and returning defender Lucas Neill on the bench for the crunch match, and was keeping his cards close to his chest Friday.

All three players were outstanding in the World Cup game against Japan but Kewell and Cahill have been more effective here as substitutes, while Neill is available after serving a one-match ban for his red card against Iraq.

Arnold would only say that everyone is fit and the mood in the camp is buoyant after their 4-0 thrashing of Thailand in Bangkok last Monday.

"In training, we've played enormously well in the last few days. The players are in an extremely good mood," he said.

"Everyone is fit (except for the suspension of Luke Wilkshire). We have a special team spirit. We're looking forward to being very successful tomorrow."

Australian captain Mark Viduka sees Japan as the clear favourites, but warned the Socceroos would rise to the occasion.

"Traditionally, the Japanese are good as a team, collectively," he said.

"There are quick players and technical players. Their last game was a tough game.

"I think definitely they are favourites, but we also are quietly confident.

Osim knows that stopping striker Viduka will be key to success, with his side much smaller and less physical than the Australians.

"The thing is how to solve the problems of physical size and techniques. These are the two questions for Saturday's match," he said.

"For example, I think about how to stop Viduka.

"In reality, the same players may be assigned to block Viduka as they did last year. But there are other players in the Australian team too.

"They are formidable when they play collectively. They are better in terms of individual capability."

Once again he will be relying heavily on Celtic star Shunsuke Nakamura and Frankfurt striker Naohiro Takahara to steer his side to a semifinal against either Saudi Arabia or Uzbekistan.