Micky Adams has said the club had no choice but to accept the clause which means striker Leon McKenzie will miss both matches against his former Norwich City club this season.
Speaking to the CET, Adams, who along with the board, would have faced more wrath from City supporters if nobody had signed on transfer deadline day said: "It was written into the agreement with Norwich and something they insisted upon.
"It is quite unusual, particularly the second game, but it was a deal breaker and I took the view that he is signing for three years and not just for two games. "So we will live with it and remember it!
No Choice Says Adams
"It wasn't a surprise that they insisted on it for this Saturday and I admit that I would have done the same, for example if Gary McSheffrey had been coming back here a week after signing for Birmingham.
"But the away one is a new one on me, but we just have to swallow it and get on with it. "As far as I know Gary can play against Coventry, but I didn't do the deal."
"But the away one is a new one on me, but we just have to swallow it and get on with it. "As far as I know Gary can play against Coventry, but I didn't do the deal."