The 71-year old Scotsman will retire from his Manchester United post at the end of the season with Shiels full of praise for a man who has achieved an enormous amount during 26 years at Old Trafford and close to four decades of management.
"Everybody takes inspiration from someone - that's what keeps us living," the Killie boss said.
"He is one of the people you look up to, especially with what he has achieved and what he has done for such a fantastic club.
"He's a unique person. There's no such thing as being irreplaceable - but he probably is.
"No-one will manage a club of that magnitude for 26 years. No-one will do that again because of the way football has gone."