"David is struggling at the moment and that is yet more bad news for us," he said. "He went out to Denmark to see the specialist about a month ago and they said that he could start to do some light training work but unfortunately he is just not improving.
"We would have hoped that by now he would be stepping up to that next level but it seems the problem is going to take a while to clear up. We may even have to look at other options, possibly even surgery.
"If surgeons can get inside and see where the problem is then it could help him to finally shake off the injury. Of course, that would put him out of the game for about six weeks or so but it would be worth it. He is a valuable player for us and we want to get him back onto the pitch."