The big questions facing the Socceroos ahead of June's World Cup qualifiers against Japan in Perth on June 5 and Saudi Arabia five days later.

* WHAT'S THE EQUATION?

After a 5-1 win over Indonesia and 2-0 defeat of China, Australia, (13 points, +7 goal difference) retains the second automatic qualification spot in Group C ahead of Saudi Arabia (10 points, -2 goal difference) and Indonesia (nine points, -6 goal difference).

A win over Japan would all but seal automatic qualification, as the Saudis would need to comfortably beat both Bahrain and the Socceroos to leap into second.

If Japan win or draw, and Saudi Arabia beat Bahrain, everything will come down to the final game.

Finish third or fourth, and another round of qualifiers awaits.

* CAN THE SOCCEROOS GO UP ANOTHER GEAR?

That's the challenge Tony Popovic has thrown down to his charges.

The Socceroos have improved across Popovic's short tenure, going unbeaten in their six qualifiers, while fresh faces like Ryan Teague and Nishan Velupillay have impressed.

They started to hit the scoreboard with some regularity against Indonesia and again in the first half against China. There is every reason to believe they can kick up a gear in the June window.

* WHO WILL BE BACK IN THE MIX?

Don't expect any of defenders Harry Souttar (Achilles), Alessandro Circati (ACL) and Hayden Matthews (ankle) to feature in June.

But Australia will hope Jordan Bos (hamstring) returns, and he and others can present some selection headaches.

Riley McGree (plantar fasciitis) is yet to return to Middlesbrough's main training while Ajdin Hrustic is struggling for game time in Italy.

Connor Metcalfe (groin) is back training at FC St Pauli and will hope to force his way back into the mix.

Mathew Leckie, yet to feature under Popovic, suffered a minor calf strain in Melbourne City's final match before the break.

It is unclear when goalkeeper Joe Gauci (hip) will be back in action.

* WHO WILL START AS STRIKER?

If he can get and stay fit, Kusini Yengi appears a front runner. But that's a big 'if'.

Stalwart Mitch Duke was dropped after limited game time at club level, but rushed in for the China game due to injuries to Yengi and Adam Taggart.

Taggart started the Socceroos' win over Indonesia before succumbing to injury, while Brandon Borrello was thrown the keys against China.

Versatile Velupillay's red-hot start to life as a Socceroo should keep him in the frame, while fellow winger Martin Boyle has re-established himself.

Apostolos Stamatelopoulos (wrist) simply can't get a run at it.

Exciting Western United striker Noah Botic was overlooked in March, but if he does maintain his form and get a look in it would most likely be off the bench.