HAWTHORN faces up to half a season without one of its most important defenders, with news that Grant Birchall has hurt his knee again.

The 30-year-old was on the verge of playing once more following a previous PCL injury, but pulled up sore after a training session earlier this week.

"Grant was progressing really well and had been coping with the training loads," Hawks general manager of football Graham Wright told hawthornfc.com.au.

"His training was solid this week, but unfortunately he experienced some swelling and upon investigation, we found some cartilage damage."

It continues a wretched period for the four-time premiership defender, who played just five games last year because of a fractured jaw and then a PCL injury he never got quite right.

Birchall was only just back from a procedure earlier this year following complications from the PCL surgery towards the end of last season. He had been earmarked as the 'quarterback' of the Hawks backline following the departure of Luke Hodge.

Premiership midfielder Will Langford has also had a setback, breaking his hand at training this week, which will rule him out for up to four weeks. He was also back in full training after suffering a finger injury during the club's New Zealand training camp towards the end of last year.

The Hawks open their season on the night of Saturday March 24 against Collingwood at the MCG.