Birmingham chairman David Gold has insisted the sale of Matthew Upson will not damage the board's relationship with Steve Bruce.
West Ham snapped the defender up on deadline day for a fee which could rise to as much as £7.5million.
Bruce spoke of his hurt and devastation after losing Upson and also stated that the stopper was sold against his will.
However, Gold says the board had to act with Upson seemingly determined to depart St Andrews in January.
Gold is confident the fallout from Upson's exit will not harm the excellent relationship currently in place between board and manager.
"I spoke to Steve last night and he was very down and I don't blame him," Gold said.
"I feel down this morning. I would have liked the player to stay for Steve, the board and the fans and we were 24 hours from that being the case.
"But the nearer we got to the deadline the clearer it became the player did not want to be at Birmingham and, if a club that is more powerful and in a higher league wants a player, it does have the advantage.
"This is one of the most difficult times I have experienced but I am confident there will be no long-term damage to the special relationship we have had with Steve Bruce.
"I am very confident that will be the case. We have a fantastic relationship, we are in this together, and in the last five years have gone through thick and thin together."
Meanwhile, Gold has rejected suggestions from Upson's agent Barry Neville that the club went back on an agreement when West Ham had an earlier bid rejected.
Gold added: "No promises were made by the board regarding a figure at which Matthew Upson could be sold. We did not renege on any deal as the agent was saying."