David Hannah has been ruled out of first-team action for the next five weeks with knee ligament damage.
United's vice-captain was hurt in the fifty-first minute of Saturday's defeat by Livingston and had to be substituted, with subsequent checks showing the injury to be serious.
"It is quite a bad one and we are talking about something like five weeks before we can expect to have him back," he said. "It's a loss for us because Dave Hannah is an important member of our team. I'd even go so far as to say that if he had still be on the park on Saturday, we would not have lost.
"He is very enthusiastic, gets in about people and, as well as stopping the other team playing, he is always liable to get into their box and score a goal."
"It's unfortunate for Hannah, but now I will be looking for players like Ronnie O'Brien, Tassos Venetis and Hugh Davidson to show they can become big players for the team. Right now we've a few who are on the fringes and for some of them the time has come when they have to show they can be first team regulars."