The 76-year-old 18-time major winner, says everything changes when a sportsman decides to tie the knot and have a family, and which often detracts from the focus of playing professional golf.
McIlroy announced earlier this year that he and fiancée Erica Stoll are currently planning their wedding for the summer of 2017.
And Nicklaus has issued a warning to the 27-year-old from Northern Ireland, telling the BBC: "When you are young and single, and one dimensional, you pretty much can do things at your leisure.