Socceroos medical staff are sweating on news from Premier League club Huddersfield to determine if star midfielder Aaron Mooy's Asian Cup is over.
The 28-year-old reportedly injured his knee during the Terriers' 1-0 loss to Arsenal on the weekend.
Scans have revealed a medial ligament injury, according to a News Corp Australia report on Tuesday.
But Australian officials were unable to confirm what, if any, injury Mooy has sustained with senior physiotherapist Phil Coles awaiting further updates from Huddersfield.
If Mooy is injured, coach Graham Arnold faces a selection conundrum when he names his 23-man squad for the tournament next week.
A four-to-six week recovery means Mooy would certainly miss Australia's opener against Jordan on Jan. 6, and possibly the other group stage matches against Palestine and Syria.
Mooy could however be fit to play in Australia's knockout matches if Arnold deems him too vital to leave out of his squad.
Former Socceroo Archie Thompson said if Mooy is unavailable it will be a big blow to Australia's hope of retaining the title.
"You want that quality. You want that leadership," Thompson told Fox Sports.
"He's playing in a top league, playing week-in and week-out so his experience is invaluable. I hope that it's not as serious as we're hearing."
If Mooy is selected but unavailable for the group stage, it will put him in a similar situation to Tottenham star Son Heung-min.
The South Korean winger will sit out his country's first three matches in the United Arab Emirates after his national association came to an agreement with Tottenham but will represent the Taeguk Warriors from the round of 16 onwards.
Fellow midfielder Tom Rogic has also reportedly suffered a knee injury but Socceroos staff are confident it won't affect the 25-year-old's hopes of playing in the tournament.
The Socceroos have already lost young gun Daniel Arzani after the winger suffered an ACL injury last month on debut for Scottish club Celtic.