Geelong's first-year ruckman Nathan Vardy will undergo immediate hip surgery, putting his AFL finals campaign in doubt.

The 20-year-old big man is expected to miss a month of football, the second-placed Cats said on Monday.

Vardy received a knock to the hip during Geelong's round-21 win over Adelaide a week ago.

"Nathan is a bit unlucky that the knee he copped has resulted in the injury at this time of the season," Geelong's general manager of football Neil Balme said.

"Our medical department looked at the options including the hip undergoing surgery to give Nathan the best option to be fit and to play in the finals.

"In the end, the best course of action was for Nathan to have surgery on the hip. The minimum recovery time is four weeks, which will put his best return date around the preliminary final.

"He's had a good first year so it's unfortunate for Nathan that the timing of the injury is so close to finals."

Vardy has kicked six goals in nine games in his debut season and he averages 6.9 disposals and 11.6 hitouts per game.

The injury to Vardy adds to the intrigue over Geelong's ruck-forward combination for the finals.

Veteran forward Cam Mooney will serve a one-match suspension when the Cats host Sydney at Skilled Stadium on Saturday and Geelong will play competition leaders Collingwood in round 24.

Brought to you by AAP © 2024 AAP