Winger Mathew Leckie may not be ready for Australia's round of 16 clash with Uzbekistan at the Asian Cup.
Assistant coach Rene Meulensteen said the 27-year-old, who has yet to feature in the Socceroos' defence of the trophy, hadn't yet proved his fitness.
Leckie was retained in the squad despite tearing his hamstring while playing for German club Hertha Berlin before the tournament.
Coach Graham Arnold believed he would return to fitness at some point after the group stages, but Meulensteen believes the Uzbekistan game could come too soon for him.
"He's touch and go, I'm not sure whether he's fine for this game because we want to eliminate every risk," he said.
"He feels he's confident stepping over that line and going … we want them to stay there for all the rest of the games, not just one. The worst thing you can do is think 'yep, great, off he goes' and boom, all the work is for nothing."
The Socceroos qualified for the knockout phase after beating Syria 3-2 in their final Group B game.
Meulensteen says the team have come back strongly from their surprise opening loss to Jordan and feels the players have grasped Arnold's attacking football philosophy.
"If you look to since Arnie and the rest of the staff have taken over, the amount of chances we've created, the goals we've scored, we are on the right track," he added.
Having played three times in 11 days, Australia's players were given a day's break before turning their attention to the game against Uzbekistan in Al Ain.
Uzbekistan qualified as runners-up in Group F, beating Oman and Turkmenistan before going down 2-1 to Japan in their final game.
Australia are 4/6 to win their next match against Uzbekistan, who are 4/1 with the draw 14/5. The Socceroos are 12/5 to win by a one-goal margin.