Sala, 28, died in a plane crash just days after completing a move to Cardiff in January as he returned to the Welsh capital having said goodbye to his former teammates at Nantes.
Willie McKay, whose son Mark was working on behalf of Nantes in the deal for the striker, arranged the flight that crashed in the English Channel, killing the footballer while pilot David Ibbotson remains missing.
Cardiff says the club “strongly reject” the claims they neglected Sala.
“He was abandoned in a hotel more or less to do his travel arrangements himself,” Willie McKay told the BBC .
“Nobody in Cardiff seemed to be doing anything. It was a bit embarrassing for Cardiff.
“They buy a player for 17m euros and then leave him in a hotel by himself to go on the computer and look for a flight – I think Cardiff let themselves down badly.
“The way they’ve acted so far, they’ve been a disgrace.”
Cardiff said in a statement: “Our club was in the process of organising a commercial flight for Mr Sala until this offer was declined owing to separate arrangements being made – the planning and specifics of which Cardiff was not privy to.
Cardiff has serious concerns over the potential unlawfulness of the journey following information that has been released. Clearly more answers as to the details surrounding this terrible tragedy are required.”
Sala’s body was found in the wreckage of the crashed Piper Malibu N264DB, which was discovered 13 days after it vanished near Guernsey. The body of pilot Ibbotson has yet to be found.
Willie McKay refuted claims that he owned the plane and suggested that he and his son Mark had been made “scapegoats” for the tragedy.
He revealed that he was alerted to Sala’s disappearance by Cardiff boss Neil Warnock, who he said “feared the worst”.
Willie McKay is not a registered agent but told the BBC that he was involved in the deal merely to help his son.
It has been claimed that Ibbotson did not possess the correct licence to be operating a commercial flight for Sala.
But Willie McKay, who organised the flight through David Henderson as he had done on “countless occasions”, said he did not know who would be operating the plane or how much it would cost.
“When you phone for a taxi you don’t ask him if he has a driving licence,” he said. “I was just thinking about getting the boy home which he wanted and we were happy with what we did.
“I’ve been told on good authority he was a very good pilot so for people to vilify the pilot after a man’s death is a disgrace. I don’t hold anyone responsible because it’s just a tragic accident.”
According to his father, Mark McKay is owed £1.5m from the deal but Willie insisted they would not be chasing the club for payment.
“This is not about money, it’s about two lives that have been lost,” Willie McKay said. “You’re prepared to lose that £1.5m given the circumstances.
“I’ve got three great kids and a wife who have been very strong though this – if others want to argue about money let them, but we won’t be arguing about money.”
Mark McKay told the BBC that the incident had made him question his future as a football agent.
“I wish I had never gone to watch the guy play,” said Mark McKay. “I wish I had never known anything about it in the first place.”