Former Western United centre-back Dylan Leonard is among 12 players including stalwarts Jackson Irvine, Jordy Bos and Martin Boyle added to the Socceroos' train-on squad.
Leonard made his debut for Schalke in the Bundesliga 2 last month after joining the German club following the hibernation of A-League outfit Western United.
The teen has been playing as a defensive midfielder after featuring as a centre-back in the A-League.
In pleasing news for Australia, midfield stalwart Aiden O'Neill also joins the training squad despite suffering an ankle injury when playing for MLS club New York City FC on May 3.
O'Neill has been a consistent starter in recent international windows.
Cammy Devlin, yet to play under coach Tony Popovic, heads into camp after he and his club Hearts fell devastatingly short to Celtic on the weekend in the match that decided the Scottish Premiership.
Irvine and Metcalfe join the Socceroos after their own heartbreak. FC St. Pauli were relegated from the Bundesliga on the weekend.
Popovic has now named 31 players in the squad for training camp in Saratosa, Florida, ahead of the World Cup which starts on June 12, with players drip-fed in as their respective club seasons finish.
A final 26-man squad must be selected by June 1 ahead of Australia's group matches against Turkey, the United States and Paraguay.
The 12 players added to the squad are Leonard, Irvine, Bos, Boyle, O'Neill, Connor Metcalfe, Cameron Devlin, Ante Suto, Gianni Stensness, Jacob Italiano, Jason Geria and Milos Degenek.
Stensness has previously not been called up by Popovic, while Suto is yet to debut.
The latest call-ups join the players already in Florida: Aziz Behich, Patrick Beach, Daniel Bennie, Raphael Borges Rodrigues, Brandon Borrello, Cameron Burgess, Anthony Caceres, Nick D'Agostino, Mitch Duke, Joe Gauci, Ajdin Hrustic, Nestory Irankunda, Paul Izzo, Mathew Leckie, Hayden Matthews, Alex Robertson, Harry Souttar, Mohamed Toure and Nishan Velupillay.
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