David Low, a Glasgow businessman, devised the strategy that helped McCann take over the Parkhead club, which was only eight minutes from financial ruin with an ultimatum from the Bank of Scotland running down. McCann paid the bank £1m up front and then went on to replace the board at Celtic.
However, Low said: "I actually believe Celtic face a bigger crisis now than they did in the early nineties.
"The team which I had started to go and see during the sixties was experiencing an upswing under Jock Stein," added Low. "There were the two European Cup finals and the losing semi-finals too. I see no prospect of Celtic competing at the same level."
Low said that Celtic could only prosper by somehow leaving the Scottish league set-up but admitted this escape route was closed by UEFA regulations that show little sign of being changed.
"Celtic are trying to run up a down escalator and that is extremely difficult," said Low. "I fear the Scottish league set-up could become more like the Irish league with part-time players and a feeder route for the leagues in England."
He said that the problem facing Celtic also confronted such clubs as Benfica in Portugal and Ajax in the Netherlands. "The financial model is broken in some countries and clubs are just trapped by the geography," said Low.
Low, who devised the strategy of achieving share proxy support for the successful bid to dislodge the Celtic board in the 1990s, said of the revolution at Parkhead under McCann: "All those tough decisions that he and the board had to make have been proved to have been sound as a pound."
He added of McCann: "He is synonymous with good business practice but there was more than that. He did not screw anybody either. The fans bought the shares at the same price as Fergus. He was honest in all his dealings and that is unusual in business."