Cornes, 29, cast a forlorn figure on the bench in the second half of Sunday’s loss to Collingwood, sporting icepacks on both his knee and calf.
The calf strain alone would have cost the dual All-Australian two or three weeks on the sidelines, so the club has made the decision to correct a nagging knee injury at the same time.
Cornes, who struggled with the same knee last season, will have surgery on Tuesday to uncover the extent of the damage to the joint.
In another blow for the Power, Matt Thomas will also miss a month with a strain of his posterior cruciate ligament.
Daniel Motlop (ankle) is rated as a ‘test’, while Justin Westhoff could line-up in the SANFL having overcome a broken foot.
