Nicoski suffered the injury in the third quarter, when his shoulder popped out of the joint.
The club is yet to put a time frame on his recovery but the West Coast website refers to him being unavailable "for at least the next few weeks".
Tom Swift is another in doubt for Sunday's match against the Western Bulldogs.
The young midfielder will be assessed after he was a late withdrawal for the Tigers' game due to illness.
The pair join an already significant casualty list for West Coast that includes first-choice players Daniel Kerr, captain Darren Glass, utility Sam Butler, and midfielders Adam Selwood, Luke Shuey and Chris Masten.
Masten is the only player likely to be available for selection against the Dogs, although he is expected to come through the WAFL first.
