Geelong big man Nathan Vardy has ruptured the anterior cruciate ligament (ACL) in his right knee and will be sidelined indefinitely.

Vardy suffered the injury at training on Saturday morning. He underwent scans that confirmed the damage to his knee.

"Obviously this is tremendously disappointing for Nathan and the team," Geelong's general manager of football Neil Balme said.

"As is often the case, the injury happened in an innocuous situation at training. Nathan and our medical team will consult with specialists ahead of surgery to repair his knee. At this stage we do not have a timetable on surgery.

"Nathan had enjoyed a really good preseason and has shown that he can compete and play well at AFL level."

Vardy debuted in 2011, playing nine games. He missed the finals that year after suffering a hip injury. He didn't return to the seniors until late in 2012. Vardy re-established himself in 2013, playing in the Cats final eight games, including all three finals.

Overall he has played 21 games and kicked 19 goals.