The ex-Newcastle player and then manager is still held in high esteem by the fans after his spell in charge from 1992 to 1997, when he lifted the club from the bottom of the old Second Division to within touching distance of the Premiership title.
Keegan has now revealed the manager's job lost its appeal after the club was set to become a Plc, prompting his shock decision to quit.
"When anybody leaves their job, it's rarely the way you want to leave," he said.
"I know it was my choice to leave, I had no option - but I was forced into a corner.
"When then chairman Sir John Hall first rang me to bring me back to Newcastle, he said 'We are the two people who can save Newcastle'.
"On the last day, he was nowhere to be seen. I felt that was bad. In fact, it was the one bad day I had there.
"I was sat in the boardroom with Freddy Shepherd, Freddie Fletcher and Douglas Hall, men I had worked with, but they said nothing as some finance man floating the club told me I had to sign a new contract or go.
"I said 'You don't know me. These people do. Thank you very much - goodbye!' It was becoming a Plc and I felt the focus of the club had changed.
"It just wasn't as enjoyable as it was."