Brisbane star Dayne Beams has been ruled out indefinitely due to knee tendinitis.
Lions’ coach Justin Leppitsch said Beams would miss at least at month, but was unable to pinpoint an exact return date.
“Beamsy won’t play round one and I am not sure past that, it could be another couple of weeks, it could be a month,” Leppitsch said.
“It is a bit uncertain the end date, unfortunately.
“It is frustrating. It can be something that can be fixed quickly in a couple of weeks or a month, but he hasn’t had the training to play the first couple of games.
“You’ve got to put a month of conditioning on top once the long term injury is fixed, otherwise they will hurt something else.”
Mathieson is expected to require surgery, but it is uncertain how long the injury will keep him out.
The Hawks have also suffered another injury blow ahead of round one, with midfielder Liam Shiels set to miss up to six weeks with a hairline fracture in his wrist.
“Scans yesterday revealed Liam has a hairline fracture in his right wrist,” Hawthorn’s GM of football operations Chris Fagan told the club’s website.
“What that effectively means is he’ll be out for somewhere between four to six weeks.
“Liam has had a really good pre-season to date and it’s a disappointing result at this stage of the year.”