Thomson played in the season opener against Dundee United but went missing for a few weeks with injury. He started, and scored, against Killie and it looked like his problems were over. However, he was an unused sub against St. Johnstone and has now torn his groin muscle, meaning he'll be out for as much as six weeks.
This is a huge blow as Thomson is one of our best central midfielders, capable of getting forward and scoring goals as well as doing the work needed at the back.
On the plus side, Paul McQuade is now back in training and could be involved in Saturday's game against Inverness Caley Thistle.