The central defender has been struggling with a knee problem. He was in the team for the side's FA Cup clash against Sheffield Wednesday, but he could not make it through the warmup.
Now Mawson knows he must see a specialist to figure out the issue.
Losing Mawson would be a huge blow, given how impressive he has been for the club since the arrival of new manager Carlos Carvalhal.
The club will be hoping he is back before the end of the season.