Ange Postecoglou believes he could pick a handful of different winning line-ups for Thursday night's clash against Saudi Arabia - but is refusing to give any clues to his preferred XI.

Australia takes on the Green Falcons at Adelaide Oval in a must-win clash for the side’s hopes of automatic qualification, with Postecoglou confirming all 23 squad members except the suspended Mark Milligan are available for selection.

PIC SPECIAL: Socceroos training in Adelaide

Adelaide-born defender Ryan McGowan arrived in camp on Tuesday night after flight delays from China and Postecoglou said his chances of playing were “very small” given his preparation.

However, the Australia coach wouldn’t be drawn on his likely starting team and claimed before Wednesday night’s final training session that he still had not decided it himself.

“They’ve given me a tough one. I’ll sleep on it tonight,” Postecoglou said. “I reckon I could come up with three or four different formations and still look like a genius.

“I’m in a decent spot. We’ve got training today. I’m always mindful to get that final training session done and dusted.

“Sometimes I’ll wait until the next morning until they’ve all woken up and been cleared by the medical crew. I always have some flexibility in my mind.”

Postecoglou has a plethora of midfield options to weigh up with Tom Rogic and Aaron Mooy both in brilliant form and both having missed the last qualifier against UAE.

Jackson Irvine was outstanding in their absence, while Massimo Luongo is also available again after missing the UAE game through injury.

The Australia boss also has a headache in defence, with the centre-back Matt Spiranovic (quad) injured, while his usual partner Trent Sainsbury is short on game-time.

Australia’s backline is comfortably the most inexperienced part of the squad and with Ryan McGowan unlikely, Postecoglou could potentially use skipper Mile Jedinak as a makeshift defender.

In addition, the goalkeeping situation isn’t set in stone, with Mitchell Langerak’s good form with German 2.Bundesliga champions VfB Stuttgart boosting his case to displace Mat Ryan.

Another factor to consider is that English Championship players such as Jackson Irvine, Bailey Wright and Massimo Luongo haven’t played competitively for a month, along with domestic-based players such as Tim Cahill and James Troisi, plus Dylan McGowan and Jamie Maclaren who’ve recently signed new deals with European clubs.

Postecoglou & Jedinak speak to the media in Adelaide

Postecoglou said the varying schedules had been well managed internally and said it wouldn’t affect selection.

“The pleasing thing for me is juggling all their schedules, some played until last weekend, others haven’t played for a month, maybe a bit longer,” he said. “Looking at them from a physical and mental stand-point, they’re all raring to go and putting their hand up, which is the most important thing.”

Postecoglou hinted he’d likely give opportunities to Bailey Wright and Milos Degenek in defence.

“We’ve got some guys at the back, Bailey Wright and Milos, guys in their early 20s who are starting to grow and playing in strong leagues now,” Postecoglou added.

“(With Ryan McGowan) He played on the weekend, so he is absolutely match fit… but it’s unfortunate he obviously had some flight challenges.

“That’s not unique. We’ve had other times where players have in a couple of days before the game and played.”

PIC SPECIAL: Socceroos training in Adelaide