They were both Scottish and they were shaped by the harshness of Scotland; Matt Busby in the mines of Ayrshire, Alex Ferguson by the shipyards of Glasgow. Both were given an early indication of what that meant. For Busby it was the General Strike of 1926 that saw the teenage miner and the rest of the pitmen of Bellshill forced hungry and penniless back to work. Eamon Dunphy, who played for Manchester United under Busby and would write his biography, said: "He had learned a lesson about trust and loyalty, about rhetoric and promise, about family and community but most profoundly about power and powerlessness."

This year, Ferguson, who grew up in the shadow of Harland and Wolff's cranes, spoke at the funeral of the charismatic Jimmy Reid who had led the workers' takeover at Upper Clyde Shipbuilders that radicalised Glasgow at a time when Ferguson, sacked by Rangers, was drifting down the divisions.

Busby was the better footballer. He played for Manchester City and might have gone to Old Trafford if United could have afforded the £150 fee in 1930. Six years later, he went to Liverpool for what in today's terms would have been £295,000. Ferguson the footballer never left Scotland and both just failed to make it in the international arena. Ferguson played for Scotland B; Busby had one international cap.

But for the Munich Disaster, the great scar over Old Trafford, both would have managed Scotland in World Cups. Once when taking journalists on a tour of the Old Trafford museum, Ferguson pointed to a picture of Busby training men who were obviously not Manchester United footballers. They were the Scotland squad on their way to qualifying for the 1958 tournament in Sweden.

Munich intervened and the Scottish FA decided not to bother with a manager. They finished last in their group, a fate that would befall the 1986 squad in Mexico, the one that could find no place for Alan Hansen, who captained Liverpool to the Double. Ferguson never had a Munich, no manager apart from Busby has had to cope with the shattering of his squad; only Kenny Dalglish dealing with the aftermath of Hillsborough comes close. You could compare it to the great Torino team, destroyed in the Superga crash in 1949. But they were all killed; there was nothing left with which to rebuild. He was back where he had begun in 1945 with OldTrafford a bomb-site and theStretford End flattened. He contemplated retirement but, like Ferguson in 2002, was talked out of it by his wife.

The United that Ferguson was bequeathed had not finished lower than fourth in four seasons under Ron Atkinson. It was already the biggest brand in world football, despite its lack of championships. His supreme achievement is not to be found at Old Trafford but 350 miles to the north east at Aberdeen. To take a small, provincial club that saw nothing of the city's oil money, smash the Glasgow cartel and beat Real Madrid in a European final was close to genius.

Neither Busby nor Ferguson were geniuses in the sense of a Brian Clough, Jose Mourinho or Bill Shankly; their lives were too balanced, they had a hinterland away from football. Like Jock Stein, a friend to one and a mentor to the other, they were wonderful observers.

To take one example in the final game of the 2007-08 season; Manchester United found themselves at Wigan, needing to match Chelsea's result against Bolton to retain the championship. It is raining and United are labouring. Ferguson sends on Ryan Giggs "because he is outstanding on a wet pitch". Giggs scores, almost rolls the ball into the net. Three of Ferguson's four European trophies have been won in the driving rain.

Neither were great coaches. Charlie Mitten, part of Busby's first United team that won the FA Cup in 1948, claimed Busby's technical knowledge was "zero". His great skill was in "geeing people up". Ferguson's greatest triumphs have all been alongside a high-class coach, whether that was Brian Kidd, Steve McClaren or Carlos Queiroz. Both were dogged by questions of the succession. Busby left behind an ageing, bickering squad with which he interfered constantly from the directors' box.

Ferguson, whose first act on coming to Manchester was to buy every book on United he could find, has spent the last years of his reign bringing young footballers to Old Trafford. He was probably more receptive to ideas. Would he, like Busby, have turned down George Best's request in 1972 to be made captain and have a team built around him?

Both were blessed with a fabulous memory. Ferguson's most famous half-time talk in the guts of the Nou Camp when United were being beaten by Bayern Munich: "You'll pass six inches from that Cup and you won't be able to touch it," was something his one-time striker at Aberdeen, Steve Archibald, had told him when asked what it was like to lose the 1986 European Cup final with Barcelona. Both knew how to play the boardroom. Louis Edwards, the man who ran Old Trafford during the glory years of Best, Law and Charlton, was Busby's own nominee. He did as he was told. His son, Martin, chairman for much of Ferguson's reign, may have been in the words of one fellow board member: "Not the sharpest tool in the box," but he knew when to delegate. He did not, as many would have done, fire Ferguson after the 5-1defeat at Maine Road in 1989.

And yet they could get it badly wrong. Without Ferguson's flirtation with horseracing magnates JP McManus and John Magnier, a relationship that soured, United might still be a debt-free plc. Busby's insistence that Tommy Docherty had to pay with his job for his relationship with the wife of the club physio, ushered in four dark years under Dave Sexton.

Both men were fascinating in their response to fallow periods. In his biography of Busby, A Strange Kind of Glory, Dunphy, who came to United in 1960, relates how footballers, cynical, embittered and unsuccessful, mocked him on the team bus. "Old Bollock Chops," they called him. Nobody called Ferguson that but the summer of 2005 found him in Beijing on a laborious, bad-tempered pre-season tour of Asia. Ferguson had just had a monumental row with Roy Keane, United were in the middle of a three-year trough, the club had just been taken over by the Glazers and his closest journalistic friend, Hugh McIlvanney, would urge him to retirerather than "be fired by fax from Florida". And both men responded not with retirement but with a thrilling wave of brilliant football centred around Charlton, Best and Law in one era and Wayne Rooney and Cristiano Ronaldo in another that culminated in two European Cup triumphs 40 years apart; a strange kind of symmetry for men who could claim to be respectively the father of Old Trafford and its big brother.

How the greats compare, by Pat Crerand

Sir Matt was a hard man, he had to be.

When he came to Manchester it was provincial even by English standards and he turned it into the world's football capital. Wherever I go with United, you find the names of George Best, Denis Law and Bobby Charlton known across the globe. That's Sir Matt's legacy.

He did not socialise with the players but you would bump into him most weeks in a restaurant. Manchester in the 1960s was full of cabaret clubs where players could go and not be bothered by people with mobiles and cameras.

But he would know on Monday morning where you had been.

Sir Alex is very much in that mould; he misses nothing. In away games or on tour he will have a laugh with the players, have a quiz with them in the hotel but there is a dividing line. You can see the shutters coming down when one of his players has overstepped it.

Sir Matt would have loved Old Trafford now. He was an innovator. Years before rugby ever got hold of the idea, he was advocating sin-bins. He had corporate boxes built at Old Trafford in 1966; he was fascinated by American sport and how they marketed the game.The present manager is like that; he has a restless, inquisitive mind.

When I came to Manchester from Glasgow it was the equivalent of coming from South America now and Sir Matt met me and my girlfriend, now my wife, with Denis Law and his wife. I don't know what Denis was doing there but I think it was because he was a familiar face with Scotland and it relaxed me.

It was those touches that made him the manager he was. It's the same with Alex; he has incredible attention to detail.

The 1963 FA Cup final was important for Sir Matt. The years before had not been good ones, United had not been a happy ship but it galvanised the club.

In the next five years we won the European Cup and the championship twice.

We knew how much the 1968 European Cup final meant to Sir Matt but we weren't nervous on his behalf. We knew we were going to beat Benfica. We had taken them apart in 1966 and we were going to do it again. I have never been more certain of a result in my life.

I am glad he lived to see United rebuilt and reborn but I have one regret.

In 1993 United played Blackburn on the last day of the season to win the title for the first time in 26 years. The trophy was presented to Bryan Robson and Steve Bruce by Rick Parry, the chief executive of the Premier League. One row behind him was Sir Matt and, if the Premier League had any class at all, they would have asked Matt Busby to present the trophy to the men who had picked up his legacy."

Pat Crerand: Manchester United 1963-1971. Commentator on the present United side for MUTV