The Scotland international has been out for three weeks with a medial ligament strain and broke down in training on Tuesday, promoting the club to send him for a scan. The results came back clear and he has been able to resume some light work but boss Peter Houston has ruled him out of the trip to Rugby Park.
He said: "The scan showed there is nothing too serious there. He won't make this Saturday but might well be back after the international break. That's what we are hoping for although we can't be certain at this stage."
He added: "He's still training on his own, doing bits and pieces, but isn't able to play in a game at this stage. He is frustrated at not being able to train with the team.
"But he'll work hard on what he can do and get treatment on the knee."
United will have Garry Kenneth back after he was stretchered off with three separate head injuries against St Johnstone last weekend.
The centre-half will have the stitches out of his various wounds on Friday.
Houston revealed: "Garry Kenneth is fine. He got a couple of bad head gashes but he gets his stitches out and we'll wrap the main wound up to protect him for the game.
"Fair play to the big man, he's not wanted to miss a minute of training and that's the attitude we want.
"To be fair the whole team showed the right attitude in what was a tough match with St Johnstone. They had to battle and they came through it with flying colours."