To progress to the semi-finals, the Socceroos must defeat the South American champions, but even that might not be enough.                                           

While Ange Postecoglou’s side are insistent that they remain focused on the present tournament, the clash with Chile will also be the team’s final game before a decisive qualifier away to Japan.

If a heavy defeat dents morale ahead of the Japan trip, Australia might not be returned to Russia next year.

Here are five things to watch at the Spartak Stadium.

1. Who will face Chile?

Ahead of his team’s third match in seven days, Postecoglou was up-front about the likelihood of changes to his starting line-up.

“Everyone is fit but we will have a check of fatigue levels,” the coach said. “The last game took a fair bit out of us considering we had a day less rest. Recovering has been very good though, the boys have been diligent.

“We will make some changes tomorrow – I will have a look at them today, give them another 24 hours to recover and then I will make the decisions.”

Will Massimo Luongo get another start?

Following his star performance against Cameroon, defender Alex Gersbach – the youngest player in the Socceroos’ squad – is likely to be rewarded with another start.

In the midfield, Postecoglou faces a real dilemma. When on-form, Aaron Mooy and Tom Rogic are two of Australia’s best players.

But Mooy looks fatigued after a lengthy season in the English Championship, while Rogic has a history of injuries.

Does Postecoglou risk both in this crunch match? Or give Massimo Luongo another chance?

Similar uncertainty surrounds the three-man defence. Bailey Wright, Trent Sainsbury and Milos Degenek have all played 180 minutes in the tournament to date, and their weariness is compounded by Australia’s intense travel schedule.