Hrustic, 20, was the big surprise selection in Postecoglou’s 30-man provisional squad for the crucial upcoming 2018 World Cup qualifier against Saudi Arabia, followed by the Brazil friendly and Confederations Cup.

The Melbourne-born midfielder only broke into the first team of Dutch Eredivisie club FC Groningen less than two months ago, since making seven appearances off the bench and scoring one goal.

Hrustic may be little known in Australia, having never been capped at any under-age level, but officials from Bosnia and Herzegovina, where his father was born, are well aware of his talents.

It’s understood, Bosnia and Herzegovina have tried to lure him to play for their under-age national team.

The 20-year-old’s selection comes in this context, but Postecoglou insisted he’s long been aware of Hrustic’s ability, having come through South Melbourne’s youth system where the Socceroos boss has previously spent plenty of time.

“Ajdin has been on our radar for a while obviously,” Postecoglou said.

“I’ve known him for quite a long time, I think I coached him as an 11 or 12-year-old (in a Football Federation Victoria camp).

“He’s technically very good and one we think who might benefit from being exposed to that environment.

“This year he’s had a bit of a breakthrough in Holland. He did very well in the Under-23 camp with Josep (Gombau).

“Since then he’s played fairly regularly coming on as a substitute. He’s shown some qualities there.”

Hrustic’s allegiance to Australia will only be confirmed if he plays in one of the side’s competitive fixtures, not a friendly.

Dylan McGowan is unveiled as a Pacos Ferreira player

New Pacos Ferreira signing Dylan McGowan is the other newcomer to the squad, with Postecoglou exploring new central defensive options amid a selection dilemma.

China-based centre-back Matt Spiranovic remains injured, while first-choice defender Trent Sainsbury hasn’t played all year at club level following his loan move to Internazionale.

McGowan got the nod in the squad ahead of Sydney FC veteran Alex Wilkinson as well as new Melbourne Victory signing Rhys Williams.

“Dylan is another one who has been on our radar for the past few years,” Postecoglou said.

“He’s one who’s been in contention and one I’ve mulled over.

“Spiranovic is still coming back from injury so was ruled out, so from that perspective we thought we’d bring in someone who we’ve been monitoring for a while.

“With his move to Europe he could be one that develops very well and might benefit from being in this environment.”

Postecoglou said the return of Tom Rogic was a boost having missed the last camp through injury and he said that period out may ensure his gun midfielder isn’t “jaded” after a long European season with Celtic.

The squad will be trimmed from 30 players down to 23 on May 31, with Postecoglou offering no guarantees to A-League Golden Boot winner Jamie Maclaren upon his recall.

Jamie Maclaren is unveiled as a SV Darmstadt 98 player

Ajdin Hrustic photo credit: FC Groningen