WEST Coast co-captain Oscar Allen will be sidelined for the next eight weeks as the Eagles prepare to place both the star forward and second-year midfielder Elijah Hewett under the knife in the coming days. 

After initial expectations that Allen would escape surgery, further investigations this week revealed that he had suffered cartilage damage as well as bone bruising in his right knee and would require a minor arthroscopic procedure before a period of rest. 

Hewett, meanwhile, is not recovering as well as hoped from sesamoiditis in his feet and will undergo surgery that will sideline the exciting midfielder until the middle of the season. 

The Eagles said he had not responded to the rehabilitation exercises that were prescribed by a Melbourne-based ballet therapist.  

"Further investigation and specialist review of Oscar's knee revealed that in addition to the previously advised bone bruising there is some cartilage damage," general manager of football Gavin Bell said in a statement. 

"This will require a minor arthroscopic procedure to trim the cartilage, which Oscar will undergo in coming days.

"Following the procedure Oscar will have several weeks recovery period to de-load his knee before assessing his return to training. 

"At this stage likely indications are Oscar will be out for at least eight weeks, but a follow up scan in a month will provide more clarity."

Allen underwent precautionary scans on his knee following the Eagles' match simulation against Fremantle and was then rested for the AAMI Community Series match against Adelaide. He wore strapping on his right knee against the Power on Sunday.

The key forward is almost certainly the Eagles' most important player after returning in 2023 from a stress fracture in his foot and kicking 53 goals, earning elevation to the co-captaincy ahead of this season and proving himself as an influential leader over the summer.

His absence could now open an opportunity for young forward Ryan Maric, who has been named in the Eagles' squad to take on Greater Western Sydney on Sunday at Optus Stadium. Young ruckman Harry Barnett has also been named in the extended squad and could allow ruck/forward Bailey Williams to play predominantly in attack.

Allen and Hewett are among nine players on the Eagles' injury list, with ruckman Matt Flynn (knee) and draftee Archer Reid (knee) facing at least seven and five weeks on the sidelines respectively.

Defender Harry Edwards (finger), midfielder Jai Culley (knee) and premiership pair Dom Sheed (foot) and Liam Ryan (hamstring) all are set to return inside the next month. Rhett Bazzo (groin) will start running in the next week. 

The Eagles revised their injury prevention protocols at the end of last season and secured new high performance boss Mathew Inness from the Western Bulldogs.

The club has had a process for reviewing the hardness of its training base at Mineral Resources Park, testing its two grounds weekly to ensure they sit within a safe range every week.