The circumstances that required Fahey to return to Ireland mean that he has begun a period of training with Dublin club, Shamrock Rovers, before his planned return to Blues in a few weeks time.
Explaining the decision, manager Lee Clark said: “Keith has been out of the game for quite some time so his and our interests are best served by him doing what amounts to a full pre-season and we have requested that he would do this with the top club in Ireland – Shamrock Rovers.
"I am pleased that Keith has now started this programme and I expect it will hasten his return to first-team action.”