Western derby weekend in Perth could be rocked with mounting fallout from a horror Fremantle season, with the resignation of Western Australian football legend Peter Sumich.

Sumich is understood to have advised Dockers management he will not continue beyond this season, with casualties tipped to escalate in coach Ross Lyon's support staff and playing list.

Peter Sumich has cut his ties with the Fremantle Dockers. Credit:Peter Sumich

Sumich has decided not continue in his role as coaching director and senior development coach.

At least two other Dockers assistant coaches have been advised they will not be offered new contracts in Lyon's ambitious rebuilding project from next season.