Brendan Rodgers has confirmed the worst fears of Socceroos and Celtic fans that Daniel Arzani has torn his cruciate ligament.
At a press conference in Glasgow overnight, Rodgers admitted: "Unfortunately, it looks like cruciate injuries for both Daniel Arzani and Eboue Kouassi.
"It's disappointing for them because they've been working hard to get into the team."
The diagnosis spells a lengthy stint in the treatment room and rehab for the ambitious 19- year-old flyer.
He'll almost certainly be out for the rest of this season and miss Australia's campaign to retain their Asian Cup title in January.
Arzani went down in agony on debut during the club's midweek 5-0 thrashing of Dundee, when he slipped awkwardly and went to ground clutching his leg.
He was stretchered off the ground in pain but still managed a wave to fans despite the disappointment.
He had only come off the bench 20 minutes earlier and had impressed everyone during his brief cameo with searching passes and relentless attacks on Dundee's defence.
He instagrammed fans thanking them for their good wishes but also posted a video of his foot in a boot to protect his knee as he struggled with a stairway.
It's understood the definitive diagnosis on his ACL injury was delayed by the extent of the extreme swelling around his knee.
But the initial fears conveyed by Celtic sources to the FFA have now been confirmed.