Clarke told the club's official website: "Markus is very disappointed things haven't worked out for him so far. He hasn't had enough minutes on the pitch.
"Some of that can be my fault and he can be unhappy with me. He shouldn't be unhappy with himself. He trains every day, he's a consummate professional and he is well liked in the group.
"It's been a disappointing season for him. But there are still eight games to go and there is a little bit of me hoping in those eight games Markus gets the chance to play and shows everyone what he can do."