Roy Keane has been accused of losing the plot at Sunderland by the man who ghost-wrote his autobiography.
With Sunderland in disastrous form in the Premier League, Dunphy, when asked by the BBC about his former friend, said Keane's recent media appearances belied a man "in a fog" and that his time at the Stadium of Light may well be doomed by a shift in the boardroom balance of power.
Dunphy queried Keane's mental state when he said: "He is rambling about all sorts of things and it's really ridiculous. He is in serious danger of getting relegated but I think that Roy Keane is beginning to believe the Roy Keane mythology."
Sunderland have lost six out of their last seven games. Dunphy continued: "He is pontificating on everything. He's lost the plot. I have the highest regard for him, he's a remarkable, intelligent, family man, but he's lost the plot big time.
"He hasn't had a settled side and I think he is in a fog at the moment. Everyone gets there at some point in your life, when things get too much for you. You don't know where the levers for control are and he's making some really silly decisions. He paid all that money for Anton Ferdinand and dropped him. Then there is [El Hadji] Diouf on the bench and out of favour."
The former Millwall player, author of a number of acclaimed books on the game, said he had felt Keane was lurching towards disaster for some time. "It has been apparent to me for the last 18 months that Roy Keane isn't going to be a serious manager," he said. "Like a lot of great players he doesn't appear cut out for management. It's becoming increasingly apparent. I just don't think he has the qualities."
Keane's transfer policy did not escape attack from Dunphy, a man known for his extended treatises on matters football on Irish TV and radio. "If you look at the remarkable, staggering number of players he has brought in and out, he has wasted a lot of money," said Dunphy.
"Maybe Roy needed to start, like [Brian] Clough, down in the lower divisions and learn the business of management and all its aspects. I think it takes two or three years to learn how to deal with directors, how to operate in the transfer market and how to set up scouting systems."
And it was a change of directors that made Dunphy feel Keane's time at Sunderland may come to an end. Irish-American financier Ellis Short is now Sunderland's new majority shareholder. Previously, Keane had the seemingly unqualified support of chairman Niall Quinn and the Drumchapel Consortium he represents. Short is understood to have questioned the team's recent performances and heavy spending on players who are yet to prove themselves in the Premier League
"Roy Keane is not a quitter," said Dunphy. "But there is a new owner and the goalposts have moved. I think the whole project is doomed."