The Socceroos are favourites for the tournament with the majority of the squad living and playing their club football in Europe.

As a consequence, though, they are not used to the humidity levels high and the threat of torrential rain storms .

"It is not easy cutting into the holiday of the players who need a rest after a long European season," Grella said. "But I think they have made a lot of sacrifices; training in some awkward conditions, clocking up some kilometres and doing double sessions.

"I think we will be getting into that first game just a little under 100%.

"I think physically the opposition has maybe a little bit of an advantage over us, being used to this climate.

"We are trying to modify our way of playing and saving as much energy as we can to get through the game."

Sunday's Group A clash will mark the first time Australia have ever played Oman.

The Gulf side have qualified for the finals only once before, in 2004, and have never made it past the first round.

But, Oman go into the game on the back of a credible 1-1 draw with Asian Cup heavyweights Saudi Arabia.

And Grella insisted Australia will not underestimate their opponents this weekend.

"Obviously we want to maximise the points we can get in the group stage," he added.

"It is important to start well, I think the respect that the Australian national team has for Oman is high.

"We will be studying them closer in the next couple of days and for us it is important to start well."