SYDNEY ruckman Sam Naismith will undergo a third knee reconstruction, leaving his football career at the crossroads.

After his latest ACL injury in mid-2020, Naismith had returned to full fitness and played two VFL games in recent weeks but he experienced some instability in his knee. 

Investigations over the past fortnight revealed the graft in his knee had failed, and he would need a third knee reco. 

Having played just two AFL games since 2017, Naismith is now expected to miss at least the next 15-16 months recovering from his latest surgery.

He is contracted until the end of 2022, but it's unclear whether he will be fit to play any of that season.

Sydney Swans general manager of football, Charlie Gardiner, said the club was "incredibly disappointed" for Naismith, who turns 29 next month.

"He has left no stone unturned in his efforts to get back to play and after a largely uninterrupted rehabilitation program, we were all looking forward to seeing him return in the back half of the year," Gardiner said. 

"Unfortunately, due to this latest setback that won't be possible. However, we know Sam remains hungry and committed to getting back doing what he loves and we will do everything possible to help him achieve that."

Naismith's latest injury leaves Tom Hickey, Callum Sinclair, Hayden McLean and Joel Amartey as talls capable of filling the ruck position. 

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