The 67-year-old begun his management career with the Magpies in 1992 and in five years created a team branded as 'The Entertainers' as they came without touching distance of lifting the Premier League title in 1996.
Spells followed at Fulham and Manchester City - either side of his England reign - before returning to Tyneside in 2008.
His second spell, however, lasted just 233 days after his relationship with owner Mike Ashley quickly deteriorated.
Keegan, in recent weeks, has further lifted the lid about his second Newcastle tenure, were he revealed he would not step foot inside St James's Park whilst Ashley remained as he doesn't want to share the same oxygen as him.
As Keegan shed more light on his future in an interview with The Guardian, he admitted a return to management is unlikely but didn't completely rule it out.
“I have had opportunities, that’s for sure," said the former England manager.
"I don’t think it’s going to happen, but when you say that you’ve got to be careful … because if someone came in like Sir John Hall did and said, ‘You’ve got the passion, I’ve got the money’, you think, ‘Wow, we could do something there’
“I’m 67, almost 68.. I wouldn’t be the oldest manager!”
Keegan left his role as national team manager a year into the job following a 1-0 defeat against Germany in October 2008, admitting that if he had not resigned, he would have been sacked.
He said: “I would have been sacked as England manager after the Germany game.
"I’d already been told by the FA that results had to improve. So I just made it easy for them."