HAWTHORN premiership defender Grant Birchall's season could be over after a setback with his injured knee.

Birchall will miss Saturday's clash with Greater Western Sydney in Launceston after experiencing swelling in his return from a posterior cruciate ligament injury.

The 29-year-old was initially expected to be out for just a fortnight, but coach Alastair Clarkson says the Hawks will consider wrapping him in cotton wool to prevent further damage.

It is dreadful timing for Hawthorn, who have already lost fellow backline stalwarts Josh Gibson to a groin complaint and Ben Stratton to a season-ending knee injury.

"He's just had a little bit of swelling attached to that PCL that he hurt against Melbourne earlier in the year," Clarkson said of Birchall on Friday.

"It's a little bit of the unknown for us, that's the unfortunate part about it.

"If that doesn't settle then he might be dusted for the year as well, but if it does then hopefully he'll only miss a week or two."

Star midfield recruit Jaeger O'Meara travelled with the Hawks to Launceston to support the team, but faces another three to four weeks of rehabilitation on his injured knee.

Goalsneak Cyril Rioli is six weeks off returning from his PCL injury, and appears unlikely to return unless the 13th-placed Hawks are in a position to push for a finals berth.