GEELONG has suffered a huge blow ahead of its AFLW preliminary final against Adelaide, with star key forward Phoebe McWilliams set to undergo surgery on Wednesday on a broken left hand.

McWilliams dislocated two fingers on the same hand in round five, but the two injuries are unrelated.

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The 33-year-old broke her hand during a marking contest in the final quarter of Friday night's loss to her former side Greater Western Sydney.

There is the slimmest of hopes McWilliams may be available if the Cats defeat the Crows and qualify for next Sunday's Grand Final.

Geelong has a number of key forwards already in the side, with Kate Darby, Maddie Boyd and ruck Aasta O'Connor spending time inside 50 this season.

Players who will come into the mix for selection include young ruck Rene Caris, defender Georgia Clark and runners Maighan Fogas and Georgie Rankin.