Fremantle will have to take on Hawthorn's tall timber without key defender Brennan Cox after scans confirmed the backman had suffered a moderate calf strain.
Cox limped out of minor premiers Fremantle's loss to Carlton on Saturday and was immediately in doubt for the start of finals.
The 28-year-old has played just 18 of 23 games this season and will be unavailable for at least next Thursday's huge qualifying final at Optus Stadium.
"It's an unfortunate result for Brennan after an interrupted season and he'll now miss our qualifying final," said Dockers football boss Joe Brierty.
"We will assess all of the interventions possible to support Brennan's recovery and look for him to be available post our first final."
Clearly winning the qualifying final and securing an additional week off would be pivotal to Cox's hopes of featuring again this season.
Hawthorn play a tall forward line of Jack Gunston, Mitch Lewis and Mabior Chol - and have Calsher Dear plus ruckman Ned Reeves in reserve - making the timing of Cox's injury particularly frustrating.
Oscar McDonald, who coach Justin Longmuir had flagged as an option up forward, will likely need to stay in defence with Alex Pearce, while Heath Chapman may need to play tall.
