Flynn to spend up to three months on the sidelines after undergoing surgery

Flynn made the move from Greater Western Sydney (GWS) to West Coast over the off season and by all accounts he had been making a solid impression at the Eagles and was expected to play in their round one clash against Port Adelaide in a fortnight's time.

The ruckman injured himself in a routine ruck drill in the lead up to the Eagles' match simulation contest against Fremantle on Friday.

West Coast's general manager of football Gavin Bell said Flynn had suffered quite a rare injury and that he is expected to spend up to three months on the sidelines recovering.

"This is a really unique injury that experienced medical staff have rarely seen," Bell said.

"There have only been a couple of other cases similar to Matt's injury in recent AFL history.

"Post surgery he will be on crutches for a short while before starting his recovery. The expected time before his return to play is between 10 and 12 weeks. Because of the unusual nature of the injury, unfortunately, we cannot be any more specific but look forward to a fit and healthy Matt returning to the field."