Sideline Cut: Jose Mourinho might well have shivered as he contemplated the sight of Alex Ferguson looking like the loneliest man in the world.

With a face like stone, Ferguson must have been stricken not so much by United's embarrassingly early exit from the European stage as by the realisation that all the power and invincibility he nurtured over 10 years was gone.

In his shining years, Ferguson hardly spared a thought for managers whose teams he routinely crushed in the Premiership and across the continent, men whose livelihoods were as shrouded in uncertainty as his is this weekend. He has seen a lot of football men rise over his 20 years of prevailing excellence at Old Trafford and has watched them fall again, as they must.

The reason the Scot is ranked as one of the giants of modern English football is that he is as hard as nails. He enjoyed the sensation of watching a series of teams that he assembled through financial clout and an intuitive brilliance for discovering players on the threshold of greatness simply tearing weaker teams apart.

On Wednesday night, it all came full circle. That Ferguson was in his final season as boss at Old Trafford was inevitable from the minute Roy Keane walked away from the club in that devastatingly clean fashion of his. Only an extraordinary reversal of the team's play could silence the growing opinion that it was time for Ferguson to step aside before he destroyed the monument he so painstakingly built. An unlikely gallop through Europe, something similar to the success Liverpool enjoyed last year, was Ferguson's best hope.

But his team is uncertain and loose and unable to transform the brilliance and hunger of Wayne Rooney into anything meaningful. There is a sense of softness about this Manchester United that mocks everything Ferguson holds dear.

Although the players were honest in Lisbon and fought for the precious goal until the end, and although they were clearly disappointed at the final whistle, they looked like they could live with the defeat.

Rooney appears to have the same sense of deep, gnawing hatred of defeat that has always driven Ferguson. Ruud van Nistelrooy has behaved bravely and gallantly as the senior professional in an organisation that has fallen apart around him.

But only against Chelsea, with Keane's stinging criticisms ringing in their ears, did Ferguson's side play with the meanness and desperation required to transform their season. Only in that game did they truly play with anger, answering a call beyond that of mere professionalism. It might well have been Ferguson's last great managerial moment, that chill Sunday evening victory.

But Keane's lacerating words will always be associated with that game and that period, and although the Cork man watched from the stands, his fierce, competitive spirit was evident in the play of his chastised team.

On Wednesday evening, Ferguson looked like a man who suddenly realised he was trapped. In the cyclical way of these things, United's visit to the Stadio da Lux provoked inevitable memories of the nascent brilliance of poor George Best, who bewitched the locals some 40 years ago. Sport thrives on nostalgia, and there was much talk about honouring Best's memory and hope that his aura and old magic could somehow lift Manchester United's iPod generation. It did not happen, and an ordinary European side firmly ushered Manchester out of the game's prestige competition and closed the door on Ferguson's final opportunity for another tilt at glory.

That United were denied the consolation of a Uefa Cup place makes the remainder of their schedule look depressingly barren. Their season has been reduced to the usual scrap for a top-four finish and, given the delicate state of their morale and the increasing disenchantment of their fans, that is far from guaranteed.

It is not pleasant to see a man being humiliated and stripped bare by a sport that he loves. But it is not uncommon either. Ferguson inherited a mausoleum of a club when he arrived in Manchester way back in the mid-1980s, a club still trading on the reputation of the Matt Busby years. The transformation of the sedate, old English first division to the gaudy, glamorous Premiership and the aggressive, relentless combination of money and marketing driven by Sky Sports probably came at the perfect time for Ferguson and United.

But he made his own luck, with clairvoyant signings in the wayward Eric Cantona and the young Roy Keane. In players like Mark Hughes, Steve Bruce and Peter Schmeichel, he had men who looked ready to die for his cause. He was there when United produced an astonishingly strong youth team which immediately won a league title during what was supposed to be a period of transition.

Among that crop was David Beckham, the blond London boy who steadily became the most phenomenally marketable football pin-up in the world. Ferguson was responsible for a decade of excellence that facilitated the transformation of United from a humdrum football club into a streamlined and ambitious business which set the tone for other football cities. Under his watch, United actively sought to broaden their fan base with pre-season tours of Asia and America. Old Trafford was redesigned into a sleek, glittering edifice with 20,000 more seats.

There was a brief period when United looked to be so far ahead of the opposition as to make English football seem pointless. The club was floated on the stock exchange, and when it attracted sizeable investment by two Irish sports enthusiasts with whom Ferguson was friendly, it seemed a perfect marriage of business and sport. And it tickled us in this country to think that two local boys could part-own United, a club with a tremendous Irish fan base.

Only three or four years ago, it seemed certain Ferguson would bow out to a standing ovation, leaving his beloved club in fine fettle to a carefully appointed successor. Now, premier players like Michael Ballack are turning away from United, and it seems probable the club will be hard pressed to hold on to Rooney.

How sour it has turned. Nothing really good has happened to Ferguson since he decided that Beckham's very strange and public celebrity lifestyle was more trouble than it was worth. His keenness to ship the often-derided midfielder to Real Madrid was based not so much on football as personality.

And although the £24 million the Spanish team laid out for Beckham seemed daft at the time, Ferguson blew that and more on the lamentable Rio Ferdinand.

Ferguson's humiliating stand-off with his Irish friends over a race horse did not reflect well on his judgment, and may have caused the early strain on his relationship with Roy Keane.

He was flinty enough to hold a perfectly composed press conference just minutes after sending Keane into exile from Old Trafford, but the brutal severing of that once great alliance weakened Ferguson greatly.

How he must have silently wished for Keane out there on the field on Wednesday night. As it is, the Irishman has yet to play his trump card and Ferguson will probably allow himself a private laugh if his great general ends up wearing the white of Madrid, a survivor to the last.

Keane can look back at his Manchester United days with a clear conscience. When Alex Ferguson leaves, he will rightly be proclaimed as one of the great managers.

But, fatally, he may well have failed in his duty to leave a great club in his wake.