He said: "Celtic have taken a chance and we are disappointed with how it has been dealt with by them and other parties.
"I am not impressed with the way Celtic have gone about it. The agent of the player has dealt with it poorly as well. Ben can do what he wants. You want people who want to be at your football club.
"Ben is a young player and he has developed well, but only over a short period of time. He has to prove himself over a far longer period than he has with us.
"In many respects, we have given him more opportunities than he would have had elsewhere. You run the risk with all players who are coming into the last year of their contract.
"We will receive compensation, which is a lot more than we thought we would receive six months ago for Ben. However, in the last two months he has done well and, if he continues to do well, he might go on to be a lot more valuable."