HAWTHORN defender Grant Birchall is at least seven weeks away from returning to football after being placed on the club's long-term injury list.

The 30-year-old underwent another bout of knee surgery in March and has slowly been ramping up his preparation for a return.  

With the long-term injury list requiring a minimum six-week stint, Birchall's earliest potential return will be pushed back to round 13, with both the AFL and VFL having a bye the week prior.

"He's progressing well but we more or less have to put a pre-season into him," coach Alastair Clarkson said on Friday.

"He's actually recovered from his knee arthroscope, that wasn't the significance around why he'd missed 10 or 12 weeks before he played again.

"He's been unable to get a training block of about 10 weeks which you need to, to prepare yourself for a season.  

"He's in the midst of doing that training block now. He's starting to feel better about his progress, we're hoping that somewhere around the bye he'll be available to play for us." 

A club's decision to place senior-listed players on the long-term injury list only assists the promotion of Category B rookies. 

Under 2018 rule changes, all traditional rookies are eligible to play senior football without being promoted.  

Hawthorn, however, has three Category B rookies – Conor Glass, Conor Nash and Changkuoth Jiath. Due to list sizes, Glass has already been promoted and played two AFL matches in 2018.

With Birchall now on the long-term injury list, it provides Hawthorn the added flexibility to promote Nash or Jiath to make their AFL debuts.

Birchall played just five games in 2017, missing early in the season with a broken jaw and the second half of the year with a PCL injury.