Darnall-born Badger, a wonderfully-consistent and classy right-back, was one of the Blades' greatest ever players and made 541 appearances between 1963 and 1976.
Raised in Tinsley Park, Badger represented both Sheffield Boys and England Schoolboys before joining his beloved Blades, firstly as an apprentice before finally signing a professional contract in August, 1962.
He made his his full league bow in April, 1963 against Leyton Orient and was capped by England at every level apart from in the seniors.
Badger - part of splendid full-back's union at Bramall Lane with Ted Hemsley operating on the left - was a member of Sir Alf Ramsay's World Cup 'Shadow Squad' of 1966, the same year that he was made captain of the Blades and became the youngest leader in the history of the club.
He was a key figure in the revered 1970-71 side who achieved promotion to the top-flight under John Harris and ended his career at Chesterfield in the mid to late Seventies.
A Blades statement read: "Len was one of the greatest full backs to play for the club, but he was also one of its greatest characters. Those fortunate to know him will testify that he was one of the funniest, warmest and kindest people you would ever have the joy of meeting.
"He loved the Blades beyond measure. He never wanted to play for anyone else, and it was possibly that loyalty to one of the more unfashionable clubs that cost him a far more glittering career, but that mattered little to him.
"He was proud of the fact he was a Blade, and you could find no other former player with not only an encyclopedic knowledge of the games he had played in, but in the history of the club full stop. He cared and it mattered.
"For many years he has been a friend and colleague to us on matchdays, playing the role of host to perfection, something he learned over many successful years in the licensing trade after hanging up his boots, and looking after the matchday guests and sponsors and making their day just a little more perfect.
"One of our floodlights has truly gone out for the last time, and it will never come on again. Our thoughts go out to his wife Mal, Sam, Stephen, and all his family and friends at this truly devastating time.
"Thanks for the memories, the stories and the service you have given to us all. God bless you, Len!"