WEST Coast ruckman Matt Flynn faces up to 12 weeks on the sidelines after undergoing surgery to repair a detached tendon where his hamstring meets the knee, delivering a blow to the club's ruck and forward plans to start 2024.

The 26-year-old, who has impressed since joining the club from Greater Western Sydney as a free agent, suffered the injury during a routine ruck drill at the club's captain's run on Friday.

Flynn jumped into a ruck bag towards the end of a light session and complained of pain around his knee and upper shin.

Scans revealed the extent of the injury and he was scheduled for surgery to expedite his rehabilitation and recovery.

"This is a really unique injury that experienced medical staff have rarely seen," football boss Gavin 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."

The injury leaves Bailey Williams as the team's No.1 ruckman, delaying plans to send the 23-year-old into the forward line more permanently to support Oscar Allen as an additional tall target.

The Eagles start their campaign in three weeks with a round one clash against Port Adelaide at Adelaide Oval on March 17.

The Eagles have suffered several setbacks this pre-season, with Jack Darling (hamstring), Dom Sheed (foot), Elijah Hewett (foot), Liam Ryan (hamstring) and Tyler Brockman (knee) all unavailable for Saturday's clash at Mineral Resources Park.