Fran Karacic may never have stepped foot on Australian soil but should the Croatian-born defender start for the Socceroos at the 2018 World Cup in Russia, he'll be doing so in the shirt he was synonymous with growing up.

The 21-year-old uncapped fullback was the bolter in the preliminary World Cup squad named by Australia coach Bert van Marwijk on Monday who regards Karacic as a potential solution to the Socceroos' problematic right back role.

Bolt from the blue: Fran Karacic in action for NK Lokomotiva Zagreb. Credit:Twitter

He holds an Australian passport due to his father's country of birth but has never travelled down under. Nevertheless, Karacic has displayed a close affinity for the Socceroos since he was teenager, according to his former teammate, Newcastle Jets defender Ivan Vujica. It wasn't his tireless style of play that made Karacic stand out during his early training sessions at Lokomotiva Zagreb, but his choice of attire.

"He always wore this Australian shirt to training - a Socceroos top. I never saw anyone else in Croatia wearing a Socceroos’ shirt but he used to wear it to training quite often," Vujica said. "That was my first connection with anyone in the team."