GEELONG has confirmed young midfielder Brent Prismall will undergo a full knee reconstruction after scans revealed a ruptured anterior cruciate ligament on Monday.

The 22-year-old suffered the injury during the first quarter of Sunday's 58-point qualifying final win over St Kilda.

He was running for the ball and attempting to evade Robert Harvey in the left pocket of the MCG when his right leg buckled underneath him. The youngster then left the field on a stretcher.

After the game, coach Mark Thompson said the club was already fearing the worst, with closer examination on Monday confirming as such.

The 25-game player will undergo the reconstruction later this week.

In better news for Geelong, the Cats are confident premiership forward Paul Chapman will be available for their preliminary final encounter with the winner of Friday night's Western Bulldogs-Sydney Swans clash in just under a fortnight's time.

Chapman left the field in the third quarter of Sunday's game with hamstring and quad troubles, and spent the rest of the afternoon on the bench icing his legs.

Scans on his hamstring on Monday were clear, and the hard-nut 26-year-old will train over the next two weeks ahead of a fitness test before the game.

James Kelly, who has missed the past three games with a quad injury, will also be tested ahead of the preliminary final.

And speedster David Wojcinski is sure to be in line for selection after playing two VFL games before the Cats' season ended the weekend before last. He hasn't played senior football since round 15 after battling an achilles problem.