Greater Western Sydney GIANTS forward Jonathon Patton will miss the rest of the AFL season after tearing the anterior cruciate ligament in his right knee against St Kilda at Star Track Oval Canberra.

Patton injured his knee during the second quarter of the match and immediately left the field and took no further part in the match. Scans later revealed a torn ACL.

GIANTS General Manager Football Graeme Allan said it was very disappointing for Patton and the club. 

"Jon worked very hard during the pre-season to get himself fit and had shown what a talented young player he is after missing a large part of last year because of surgery to his left knee," Allan said.

"To suffer another serious knee injury so soon is a cruel blow. Naturally the whole club is right behind him and we will fully support him as he undergoes surgery and through his recovery.

"We have every confidence that he will work just as hard again to get back to full fitness and his absence is an opportunity for other players at the club to step up."

Allan said the club and Patton would determine the best course of action for his rehabilitation.

Patton has played 10 games and kicked nine goals for the GIANTS since he was selected with the number one draft pick in 2011 NAB AFL Draft. He recently re-signed with the GIANTS until the end of 2015.