Holger Osieck says Lucas Neill must find a club and play regularly if he is to earn a place on the plane to Brazil next year.
Neill, 35, performed strongly as Australia collected seven points from their final three games of World Cup qualifying, booking their place at the 2014 tournament.
That was despite the veteran centre-back being without a team since ending a short spell at Sydney FC late last season.
According to Osieck, the key defender is absent from the Socceroos' camp at the East Asian Cup as he negotiates a deal to play in Major League Soccer.
But the German did admit Neill's struggles to secure a contract have been weighing on his mind.
"It is a concern," he said.
"If he hasn't got a club and he's not playing, how can you play for the national team? I think he is aware of that."
The outlook in the short term is more positive for Harry Kewell, as Osieck prepares to pay close attention to his form with Melbourne Heart next term.
"Whoever plays, whoever performs, has a chance," he said.
"No matter what his name is, no matter what his position is, what his club is. It's about performance.
"Due to the fact he's back in Australia, it's very easy to follow up on him."
Left-back remains a problem position for the Socceroos, prompting Osieck to confirm Ivory Coast-born Adama Traore will be under consideration for selection if he becomes an Australian citizen.
"We will definitely have to monitor him closely," he said.
Aziz Behich, who played in Australia's qualifying campaign for the East Asian Cup last December, is another potential solution to the problem at full-back.
Behich has returned to Heart on a season-long loan from Bursaspor after struggling for playing time at the Turkish club.
"He had been part of our group in Hong Kong, which was not the same level of players as we are facing here," he said.
"He now gets the opportunity, he will hopefully play regularly. The A-League gets more and more competitive, so I think it's a good ground for development for players like Aziz. It is to be hoped he grabs his chance."