Ryan last played for the Eagles in Round 3 and has since battled with the injury throughout the course of the year, with any return anticipated to come through the final weeks of the home and away season.
On Tuesday the club confirmed the 26-year-old would not be risked through the final seven rounds after meeting with a specialist, who has suggested surgery for the hamstring issue.
“Liam has had a number of specialist opinions and the medical advice is he will need further surgery on his hamstring, and that will happen at some stage next week,” Wes Coast's head of health Mark Finucane said in a club injury update.
The experienced duo will add much-needed leadership to Adam Simpson's side for Round 18 when the Eagles host Richmond at Optus Stadium. They could be joined by Greg Clark (foot), Callum Jamieson (hip), Luke Foley (hamstring), Samo Petrevski-Seton (quad), Zane Trew (concussion protocols) and Isiah Winder (knee) in the selection mix for this weekend.
“(The group) had a really good group session together with the development coaches on Friday and that has set them up nicely to return to play this week."
Hampered utility Elliot Yeo won't return this week from a hip injury that has kept him out of action in recent weeks, however he will look to build his workload with the aim of a comeback occurring soon.
“Elliot has a really important week to guide the direction of his rehab progression. Hopefully he can get a bigger session later in the week and then we'll see how he is for the next week or two after that."
West Coast will face Richmond at Optus Stadium on Sunday at 2:40pm local time.