Volpato switches Italy for Socceroos as Cup cull looms

Volpato, who was born and raised in Sydney and played his junior football at Sydney United 58, Sydney FC and Western Sydney before moving to Italy, represented Italy at U19 and U20 level.

The 22-year-old, who has scored seven goals in his three seasons with Sassuolo after two seasons with fellow Serie A club Roma, said in March he was "waiting for Italy" to select him for the senior side, who subsequently failed to qualify for the World Cup.

"I wish him well," Popovic said days later of Volpato's plans to defect.

Football Australia (FA) said in a statement on Friday it has now lodged paperwork to FIFA and awaits a Change of Association Clearance from the world governing body to ratify Volpato's allegiance switch.

FA has received a release letter from the Italian Football Federation and, once cleared, Volpato will be eligible to represent Australia.

The Socceroos know one thing ahead of their trip to the Rose Bowl in Pasadena, California, to play Mexico: 30 players can't fit into 26 spots.

Australia have left their pre-World Cup training camp in Sarasota, Florida, to begin their west coast sojourn.

The Mexico match will also form the final audition before Popovic picks his 26-player Cup squad, to be submitted to FIFA on June 1.

Forward Archie Thompson was among those scrapping for a spot under Guus Hiddink at the 2006 World Cup and can relate to the current group's attempt to impress his old teammate Popovic.

"Every little bit of what you've got can improve and maybe change his mind," Thompson told AAP.

"Even putting on an Australian jersey for World Cup qualifiers, or even just friendlies are always nerve-wracking, because you want to be performing all the time, but this one just has a bit more carrot to it.

"I've been there before, it's strenuous."

Thompson is one of Australia's most recognisable footballers but didn't get a minute of game time in 2006 behind the likes of Mark Viduka and John Aloisi.

A knee injury scuppered his hopes in 2010, whereas Thompson was left out by Ange Postecoglou in 2014.

"I can definitely understand the position those players are in," Thompson said.

"There's always twists and turns in whether he might see something that he didn't see before in those camps, whether it might be football, maybe your mentality, because I know  Popa's very strong on that."

Jason Geria, Milos Degenek and Kai Trewin are among those jostling for defensive spots, along with teenager Lucas Herrington.

Forward Nishan Velupillay is a contentious option for some but, like Geria, has always performed in a Socceroos shirt under his old Melbourne Victory boss Popovic.

"He's very loyal to the players that haven't let him down," Thompson said.

Injuries have ruled out Riley McGree, Lewis Miller, Patrick Yazbek, Nicholas D'Agostino and Hayden Matthews, while Mitch Duke, Alex Robertson and Anthony Caceres were cut this week.

With Mat Ryan the clear No.1 goalkeeper and Paul Izzo looming as deputy, either Patrick Beach or Joe Gauci appears likely to miss out.

Aiden O'Neill's fitness after an ankle injury could determine whether Hearts midfielder Cammy Devlin makes it.

Mathew Leckie's late-season A-League Men form thrust him into contention, like Harry Souttar's return to fitness.

"Popa knows or has an idea about the core of what he wants and then obviously it'll be the fringe players and whether they can mould into what he wants - and maybe there's something that he's missing, or at least a back-up," Thompson added.

"It's always so difficult."

SOCCEROOS TRAINING SQUAD:

Patrick Beach (GK), Aziz Behich, Brandon Borrello, Jordan Bos, Martin Boyle, Cameron Burgess, Alessandro Circati, Milos Degenek, Cameron Devlin, Joe Gauci (GK), Jason Geria, Lucas Herrington, Ajdin Hrustic, Nestory Irankunda, Jackson Irvine, Jacob Italiano, Paul Izzo (GK), Mathew Leckie, Awer Mabil, Connor Metcalfe, Paul Okon-Engstler, Aiden O'Neill, Kye Rowles, Mat Ryan (GK), Harry Souttar, Mohamed Toure, Kai Trewin, Nishan Velupillay, Cristian Volpato, Tete Yengi