PERTH, AUSTRALIA - JULY 01: Nathan Fyfe and Michael Walters of the Dockers walk from the field after being defeated during the round 15 AFL match between the Fremantle Dockers and the Brisbane Lions at Optus Stadium on July 1, 2018 in Perth, Australia. (Photo by Paul Kane/Getty Images)

The Dockers are set to face several finals contenders without star skipper Nat Fyfe or veteran ruckman Aaron Sandilands, in what will prove to be a hellish month for the club.

Sandilands, at Sunday's disappointing 55-point loss to the Lions, was withdrawn last-minute following a calf injury in the warmup and is now out of action for three weeks.

The 35-year-old is out of contract at the seasons end, and is no certainty to play on - especially if his latest injury proves serious.

Freo's game quickly went from bad to worse once Fyfe pulled up short with a right hamstring strain in the second quarter; the club now expects his absence for at least four weeks.

The skipper received some hamstring treatment early in the match, ending the first quarter with just five disposals and a clearance - the shock loss leaving them a significant percentage adrift of eighth spot.

"We know how professional Nat and Aaron are, so we see Nat's injury being a four to five-week injury to the hamstring," general manager of football operations Chris Bond told afl.com.au.

"Hopefully, it may be sooner, it just depends on how he pulls up."

The club is in for an arduous month, with up and coming games against Melbourne in Darwin, Port Adelaide at Optus Stadium, Essendon at Etihad and Hawthorn at Optus.