Alex Gilbey will miss the rest of the season after requiring knee surgery.
The 23-year-old has made 25 appearances for Dons since arriving from Wigan on transfer deadline day in August, and very quickly became captain of the side under Robbie Neilson.
However, he reported a knee problem to the Dons medical staff after the 1-0 defeat to Walsall and after further tests, he was sent for surgery.
"After the game against Walsall, he reported the injury to us – we acted upon it and he had an MRI before visiting a surgeon in London," explained physio Simon Crampton
"Unfortunately for Alex, it was discovered that he had picked up a significant injury to his knee. The nature of the injury meant it had to be operated on – he has had that surgery and all went as well as it could do."
Manager Dan Micciche added: "It's not good. We're devastated for Alex. In the time I've been here, he has been a fantastic leader both on and off the pitch.
"We got some bad news on Tuesday that he will be out for a long period - the rest of the season.
"Our thoughts are with him, he's getting great medical treatment here. He'll be here on Saturday cheering us on."