FREMANTLE has suffered a huge blow as it fights to qualify for its first AFLW final, losing key defender Alex Williams to a torn ACL in her right knee.

Williams is a key stopper in Fremantle's backline and will be a big loss for the Dockers' virtual elimination final with North Melbourne on Saturday.

The 25-year-old suffered the injury in the second quarter of last week's win over Geelong. 

"This news is devastating not only for Alex, but also for the team. She has been doing really well this season and has been such a great contributor to the team on and off the field," Fremantle AFLW high performance manager Kate Starre said.

"The medical staff will set an outline of what takes place from here including surgery; post-surgery we will work with Alex on her rehab program."

It is the second ACL injured suffered by a Fremantle player this season, with rookie Brianna Moyes tearing her right ACL in round two. Teammate Brianna Green is still sidelined after a knee reconstruction last year.

North Melbourne forward Maddy Smith is available for selection after overcoming the patella injury which has sidelined her for the entire season.

Teammate Nicole Bresnehan (wrist) is a test for this week.

Geelong duo Anna Teague (back) and Sophie Van De Heuvel (ankle) are chances to play in the club's must-win clash with Greater Western Sydney but will need to pass tests in order to be picked.

Teammate Aasta O'Connor will be available after serving a two-match suspension.

Young Collingwood defender Iilish Ross sprained her ankle last weekend against North Melbourne and will not play against Brisbane.

Adelaide could potentially make at least two changes, with forward Jess Sedunary poised to play her first match this year since suffering a foot injury, while veteran Courtney Cramey is on track to return from a two-week hamstring injury. 

GWS will be hoping key players Nicola Barr (hamstring) and Alyce Parker (whiplash) pass tests and are declared fit for this weekend's match against Geelong.

Giants forward Jacinda Barclay is awaiting the result of scans on her collarbone, an injury suffered in a bump during last weekend's loss to Adelaide.

Brisbane forward Kate McCarthy requires scans on a potential broken nose.