WEST Coast ruckman Nic Naitanui won't require surgery to fix his ongoing Achilles tendon injury, but the star big man is set for another two months on the sidelines.

Naitanui struggled with Achilles soreness during the pre-season and he will miss a third straight game when the Eagles take on Fremantle in Sunday's Western Derby.

The 32-year-old met on Friday with medical staff, who determined a return "closer to mid-season" was the best option.

"Nic has not progressed from his Achilles issue as quickly as hoped and he will need a period of time before he can increase his training loads and build towards returning to play," West Coast's general manager of football Gavin Bell said in a statement.

"Nic has been working hard behind the scenes in the gym to build his leg strength, particularly his calves, so that when he is ready to resume playing we see the same explosive and dynamic footballer he has always been."

The absence of Naitanui has left West Coast lacking firepower in the ruck department.

The 201cm Bailey Williams is leading the ruck division while Naitanui is sidelined and 192cm forward Jake Waterman was his back-up in last week's win over GWS.

MEDICAL ROOM Check out the full injury list

The duo are set to be severely tested on Sunday when they confront star Fremantle pair Sean Darcy and Luke Jackson.

"It's probably the biggest challenge in the AFL. They're No.1 for hitouts," Simpson said.

West Coast premiership midfielder Elliot Yeo will miss another game with a calf injury, but he's a chance to return for next week's encounter with Melbourne at Optus Stadium.

Fremantle star Nat Fyfe (plantar fasciitis) fell just short in proving his fitness in time for the Derby and it's an injury he might need to manage for the rest of the season.

"He was close. He trained all of the session yesterday," Longmuir said.

"It just probably hasn't come along as well as we needed.

"It's improved but we thought the extra week would make a fair bit of difference.

"I think it's going to be a week-by-week thing. It can come good pretty quick and it might hang around a little bit longer than we expect.

"It's a hard injury to put a time frame on."

Longmuir is hopeful Fyfe will be ready to return for next week's clash with Adelaide.