Socceroos coach Holger Osieck is unsure about who will be the side's defensive linchpin when captain Lucas Neill misses their all-important World Cup qualifier against Oman in March.
Neill picked up his second yellow card of Australia's 2014 World Cup qualifying campaign in the side's 2-1 win over Iraq, a result which lifted the Socceroos to second place in Asia's Group B.
The 34-year-old was suspended for the clash with Oman, but will play a crucial mentor role in next Wednesday's friendly against Romania as Osieck mulls over who's likely to partner Sasa Ognenovski in his absence.
The Romania fixture at Spain's Estadio Ciudad de Malaga will be Australia's final hit-out before they host Oman in Sydney on March 26, a game Osieck said his charges simply "have to win".
Osieck will look to trial a slew of young defensive talent against Romania, with Middlesbrough's Rhys Williams returning from an ankle injury and Ryan McGowan, now plying his trade for Chinese side Shandong Luneng, included in the 19-man squad.
"Rhys was part of the team then he was very unfortunate to be out for a significant period, due to his injuries," Osieck said a week out from the first soccer clash between Romania and Australia.
"Now he's playing regularly again, I want to see him.
"He can play the full-back position, he can play in the centre-half. And the same goes for McGowan.
"So I definitely will have a good look at the two of them. Because in that area, there's some inexperience."
Central defenders Michael Thwaite and Robbie Cornthwaite impressed in recent Asian fixtures, while Matthew Spiranovic is currently injured.
Ognenovski was a notable absentee from the squad named to take on Romania, but Osieck said this was simply to ensure he got a good look at Neill's replacement.
"He is a regular in this team, I know what he can do for the team," Osieck said.
"If I bring in both Neill and Ognenovski then I can't test the others."
The English Premier League's Mark Schwarzer and Brett Holman will feature against Romania, but Tim Cahill was left out so he could focus on pre-season training with US club New York Red Bulls.
"Two weeks ago when I was at the Sydney FC game with Tim, we had a really decent chat," Osieck said.
"There was never a question that he would be part of the friendly."
Socceroos squad: Mark Bresciano (Al Gharafa), Alex Brosque (Al-Ain Club), Robert Cornthwaite (Chunnam Dragons), Jason Davidson (Heracles Almelo), Adam Federici (GK, Reading), James Holland (Austria Vienna), Brett Holman (Aston Villa), Mile Jedinak (Crystal Palace), Robbie Kruse (Fortuna Dusseldorf), Mathew Leckie (FSV Frankfurt), Ryan McGowan (Shandong Luneng), Matt Mckay (Changchun Yatai), Lucas Neill (Al-Wasl), Tommy Oar (FC Utrecht), Nikita Rukavytsya (FSV Mainz), Mark Schwarzer (GK, Fulham), Luke Wilkshire (Dinamo Moscow), Rhys Williams (Middlesbrough), Michael Zullo (FC Utrecht).