Aaron Mooy is set to miss out through injury, opening the door for a number of in-form midfielders, while question marks surround who can deliver goals up front.
Other positions are a lot easier to predict as the green and gold look to name a squad capable of lifting more silverware in 2019.
Literally the first name on the Socceroos team sheet, Maty Ryan will line-up between the sticks for Australia at the Asian Cup should he stay fit.
In the wings will be veteran keeper Danny Vukovic, who's having another stellar season in Europe with Genk, while Mitch Langerak looks to have done enough to keep his place in the squad after securing game time and top-flight survival with J-League side Nagoya Grampus.
Socceroos skipper Mark Milligan and Trent Sainsbury will be in the squad as they once again form Australia's centre-back pairing.
On the left will be Aziz Behich with Josh Risdon likely just edging out Rhyan Grant for the right-back spot, who will likely still be named as back-up.
Milos Degenek, Alex Gersbach and Matthew Jurman will all also likely be named as defensive reinforcements.
While under a minor injury cloud, Tom Rogic should be named and could at the very least shine off the bench for Arnold should his fitness be an issue.
Other certainties in the squad include 2015 Asian Cup star Massimo Luongo and Jackson Irvine.
The rest isn't so clear with Mustafa Amini and James Jeggo named in Arnold's last squad but failing to really catch the eye since - though Jeggo did score and produce an assist in Austria over the weekend.
Having scored the winner in the 2015 Asian Cup final, James Troisi is pushing for a recall as is Melbourne Victory teammate Terry Antonis with the duo in fine form.
Though Aaron Mooy has been ruled out of the tournament by Huddersfield, the FFA are getting a second opinion on his injury meaning he could still in theory be named.
Where will the goals come from for the Socceroos? That's the question Arnold must answer at the Asian Cup and he'll be hoping to name a squad capable of delivering.
Mathew Leckie is perhaps the only certainty in Australia's final third right now and could be deployed on the right wing or even as a number nine.
Though in mixed form for their clubs, Jamie Maclaren and Tomi Juric will also likely be fighting it out for that number nine position with both given minutes in November's friendlies.
Andrew Nabbout is fit again and though lacking game time, his versatility up front is an attractive prospect for the green and gold.
On the flanks, new boys Awer Mabil and Martin Boyle seemingly did enough last month to secure another call-up, while Robbie Kruse could miss out with a minor injury keeping him sidelined in Germany right now.
In the A-League, Chris Ikonomidis has become a hard man to ignore with his killer instinct in front of goal and adaptability across the final third something Arnold may look to utilise.
Brisbane Roar striker Adam Taggart is the current top-scorer in the competition but persistent injuries and a lack of sharpness in front of goal mean he's a long shot of being named. Craig Goodwin could also bring some different with his left foot, though his form has dipped in recent weeks. Dimitri Petratos is another waiting in the wings but hasn't done enough to demand Arnold's attention so far this season.
Potential 23-man Socceroos squad: Maty Ryan, Danny Vukovic, Mitchell Langerak, Trent Sainsbury, Mark Milligan, Aziz Behich, Josh Risdon, Milos Degenek, Rhyan Grant, Alex Gersbach, Matthew Jurman, Tom Rogic, Massimo Luongo, Jackson Irvine, Mustafa Amini, James Troisi, Mathew Leckie, Jamie Maclaren, Tomi Juric, Martin Boyle, Awer Mabil, Chris Ikonomidis, Andrew Nabbout