Australia's new 3-4-3 formation can harm opponents - Mathew Leckie

Australia are only scraping the surface of a new system which can worry opponents, according to winger Mathew Leckie.

Leckie says the fresh 3-4-3 formation deployed by coach Ange Postecoglou will ultimately prove to be one of the Socceroos' greatest weapons.

"We can be very powerful and dangerous in that formation," Leckie said in Adelaide on Saturday. "But it comes with time as well, we have only had two games to stack it up."

Postecoglou introduced the formation for Australia's past two World Cup qualifiers against Iraq and United Arab Emirates, with Leckie expecting the reshape to continue in Thursday's fixture against Saudi Arabia in Adelaide.

The Saudi Arabia game is vital to Australia's chances of direct qualification into next year's World Cup in Russia -- the Socceroos are three points adrift of group leaders Japan and the Saudis with three matches remaining.

The top two secure automatic berths with the third-placed nation pitched into a playoff, but Leckie is confident Australia can avoid the harder road to Russia.

"Saudi Arabia are in a good position on the table and we need to not just draw but win -- it's a must-win," he said of Thursday's encounter.

"We're very confident. We are very, very strong at home, just like when we go away the other teams are strong. We will definitely cause a lot of problems for them and if we play at our best, it will be tough to stop us."

Leckie joined the Australia squad in Adelaide after switching Bundesliga clubs, moving from relegated Ingolstadt to Hertha Berlin.

The 26-year-old wanted his club future settled before the Socceroos' massive month -- after the Saudi Arabia qualifier is a friendly against Brazil before a Confederations Cup campaign.

"I wanted to get it out of the way before coming into camp," Leckie said. "I have got a free headspace and can concentrate purely on this, with no worries about what is to come in the club career.

"I hadn't really spoken to them [Hertha] until the last couple of weeks so the contact came pretty late but the process was pretty fast. Obviously it's a big club and I felt it was the best option."