Having entered the match against Dundee FC in the 57th-minute and with his side cruising at 5-0, Arzani showed glimpses of the type of form that has him ranked among Australian football's most exciting prospects in years.
What shaped as an exciting start to life as a Celtic player turned to disaster as Arzani left the field on a stretcher, just 20 minutes after entering the fray.
While the 19 year-old was seen waving and smiling to fans as he left the field, reports have emerged claiming Celtic staff fear the teenager has torn his ACL. While there hasn't been official confirmation from the club, Arzani appears set for a lengthy lay-off, ruling him out of the January Asian Cup in Japan.
The injury soured a stunning win for the Hoops, with Arzani's Socceroos team-mate, Tom Rogic, kicking off the rout in the 20th-minute.
By halftime the visitors were up 4-0 and firmly in control.