The problem with living legends is just that – living. They are still around in the flesh and inevitably their successors find themselves being compared with someone who is more than a mere memory.
Sir Alex Ferguson is leaving the manager's job at Manchester United but will continue to be a presence at Old Trafford for the foreseeable future. And as United begin a new era under David Moyes next season the television cameras will waste no time cutting away to the directors' box to catch Fergie's reaction to events on the pitch, with his feet no doubt itching to charge down to the touchline.
Moyes has always been his own man, and with Ferguson's blessing on his CV would appear to be the most logical choice as the new United manager. His reputation at Everton has been acquired through an ability to keep the team respectably placed in the Premier League on slender financial resources. Now he will be expected to win things.
Filling the void when a highly successful manager of long standing retires is never easy, as United discovered when Sir Matt Busby decided to call it a day in 1969, a year after his team had won the European Cup. Busby stayed on as general manager and became a director while Wilf McGuinness, a former player who was on the coaching staff, took over a team showing their age in places and with their brightest star, George Best, starting to have drinking problems.
Busby never really went away and actually returned as manager in 1970-71 after McGuinness's short reign ended. Frank O'Farrell, a capable manager, only lasted a season before Tommy Docherty arrived to begin a rebuilding process in which United bounced straight back into the old First Division after being relegated in 1974, courtesy of a backheeled goal by a distraught Denis Law who by then had gone back to Manchester City.
Docherty's United, including as it did Steve Coppell, Lou Macari, Sammy McIlroy and Martin Buchan, appeared rich in league championship potential, but then he fell in love with the physio's wife and Busby was thought to be an influence when the Doc was dismissed in 1977. Under Dave Sexton and Ron Atkinson United promised more than they delivered and even Ferguson's team took seven years to win their first league title.
What Moyes will need more than anything is time. Before this season, which began with a win over United, his Everton teams tended to start slowly and only pick up the pace after Christmas. It is doubtful whether Old Trafford could wait that long.
Either way, Moyes will be on probation with United's followers. He will be treading the well-worn path of those who have taken over from managers who had appeared set to pick the team forever.
Some have done better than others. Billy McNeill replaced Jock Stein, who had won everything with Celtic, in 1978 and went on to win three Scottish League titles, one Scottish Cup and a League Cup during his first spell in charge at the club. Joe Fagan was 62 when he succeeded Bob Paisley at Liverpool and was regarded as a short-term appointment while Kenny Dalglish was being groomed for management. Yet in his first season the team won the league, the League Cup and the European Cup.
When it comes to establishing a managerial dynasty Liverpool have done better than most. After Bill Shankly retired Paisley was waiting in the Anfield boot room to replace him with Fagan close behind. The sequence continued through Dalglish, but ended with Graeme Souness and the championship-winning habit has yet to be regained.
West Ham United's greatest era coincided with the 28 years during which the team was managed by two men, Ron Greenwood and John Lyall, the coach who took over when Greenwood was kicked upstairs in the mid-70s. Greenwood and Lyall were at one in knowing the sort of free-flowing, imaginative football they wanted their teams to play. West Ham have never really recaptured the mood and the method of those days.
Ferguson reached that rare peak in the precarious world of football management where nobody could imagine anyone else doing the job. It was much the same with Stan Cullis at Wolverhampton Wanderers and Brian Clough at Nottingham Forest and neither Wolves nor Forest have repeated the triumphs associated with those names.
It seems fairly safe to assume that Moyes is not about to win 13 Premier League titles. But one would be a start.