Ugly scenes at Marvel Stadium on Sunday afternoon saw goal umpire Steven Piperno replaced after he was struck by a water bottle.
Piperno was in between the posts in front of the Carlton cheer squad mid-way through the second quarter when a plastic water bottle hit him in the back of the head/neck.
Emergency umpire Chelsea Roffey replaced Piperno, who was reportedly bleeding following the incident.
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Commentators quickly caught wind of the matter and were left stunned when a replay was shown via the goal-post camera.
"That is just nothing short of disgraceful," veteran broadcaster Brian Taylor said.
At half-time, Fox Footy's Jon Ralph said the patron who threw the bottle, who is not a cheer squad member, left the ground immediately after the incident.
The AFL is reportedly confident of identifying the culprit, with a life ban a distinct possibility.
Carlton entered the clash with plenty to play for - a win would assure them of finals football, while a loss would make for a nervous wait, relying on Port Adelaide to beat Fremantle in the final game of the round in order to lock in a top-eight finish.
More to come.