The manager of the club has resigned.
He was the manager for four promotions, including from League One.
"I want to personally thank him for all his hard work," co-owner Darragh MacAnthony said in a club statement.
Ferguson issued a statement through the League Managers Association saying that he had come to the decision after serious consideration.
After working hard and winning promotion to the Championship, I hope the club can find a way to stay there.
I would like to express my admiration for Darragh MacAnthony, who has supported the club for many years.
The fans will get behind him and the new management no matter what the position of the club is.
MacAnthony and his partners regard Ferguson as one of the greatest managers of this football club, most certainly in the modern era.
The success we have enjoyed with him at the helm has been unparalleled and he will always be described as a legend by myself and my partners.
After a loss at Derby, which dropped them below the Rams and five points adrift of safety, they dropped into the basement of the Championship.
The club are not sure who will take charge of the team before their next match.