Goalkeeper Adam Federici and midfielder Chris Herd have withdrawn from the Australian squad with injuries ahead of next month's World Cup qualifiers, according to Football Federation Australia.
Back-up goalkeeper Federici, whose club Reading recently won promotion to the English Premier League, has an undisclosed injury and has been replaced by German-based goalkeeper Mitchell Langerak.
Herd, who plays for Aston Villa in the EPL, will not be replaced at this stage, FFA said.
Australia will play Denmark in a friendly in Copenhagen on June 2 as a warm-up to FIFA World Cup Asian qualifiers against Oman in Muscat on June 8 and Japan in Brisbane on June 12.
Club commitments will also prevent midfielder Carl Valeri and striker Josh Kennedy being available for the Denmark friendly, with both players joining the squad in Oman.
Valeri has been given permission to play for his Italian club US Sassuolo in the Serie B promotion play-off matches against Sampdoria on May 30 and June 2. Kennedy will travel to Muscat following his AFC Champions League match for Nagoya Grampus against Adelaide United in Adelaide on Tuesday.
The FFA said Dutch-based midfielder Brett Holman was also in doubt for the Denmark match as he awaits the birth of his second child.