The 32-year-old got a knock in Aberdeen's 3-2 defeat to Inverness Caley Thistle but played on, only to discover he had fractured his ankle.
He eventually had to go off but even resumed training last week before further examination discovered the damage was far worse than first feared.
The utility player could now be out for the rest of the season.
Clark told the Daily Record: “I knew it was a sore one when it happened but I didn’t know how bad.
“I got up and ran across for the ball at the touchline and at that point I realised there was something seriously wrong.
I didn’t think it was a break though. I thought it was just a bad gash. In fact only last week I started running again but it still wasn’t right and it was only after I went for another scan they realised I had chipped some of the bone around the ankle.
“It’s pretty bad and they can’t tell me how long I can expect to be out. It’s frustrating because I was in the side and we were doing well.
Craig Brown added: “It looks like Chris is facing a considerable spell out, it could be for the rest of the season.
“It’s another huge blow. We are thin on the ground for midfielders and we are limping towards the break.
“But Hughes and Osbourne might give us a boost this weekend and we are looking to atone for the Motherwell game.”