How much will United miss Keane in the Nou Camp on 26 May? No doubt his physical presence would have been particularly valuable against such a strong and resolute side as Bayern Munich, and particularly against the threat posed by Stefan Effenberg, the German side's most influential midfielder, whose game, like Keane's, is finely balanced between skill and power, albeit in slightly different proportions.
But Alex Ferguson's campaign to reinforce his squad over the last few years has presented him with an ideal replacement in Ronny Johnsen, who played a creditable part in United's fightback in Turin. No one else in the United squad is as well equipped to assume Keane's role as a deep midfield player who breaks up attacks but can also pass the ball and occasionally get forward to provide an attacking alternative.
Of course, Johnsen does not possess Keane's bite. Few do. In a game such as Wednesday's, on a night of high intensity and resounding significance, Keane is always playing on the fine edge of the rules. Against Arsenal, United's greatest domestic rivals, this season, his bone-shuddering battles with Patrick Vieira have been something extraordinary to behold - and the best possible advertisement for maintaining a degree of physical contact in football. Keane sees such confrontations as the key to psychological supremacy. And when he has won one of them, he goes looking for another.
With his goal in the 26th minute in Turin, Keane laid the keystone of United's victory. Three minutes earlier, the tide that had swept Juventus into a two-goal lead had shown the first sign of turning when Ciro Ferrara hauled Dwight Yorke down by the shirt collar inside the area, unseen by the otherwise excellent referee. And then, after Andy Cole had won a corner on the left, Keane bustled in between Gianluca Pessotto, his marker, and Zinedine Zidane to put his head to David Beckham's beautifully flighted inswinging corner with a power and accuracy reminiscent of Zidane's own efforts in the World Cup final.
The conclusiveness of Keane's strike did wonders for United's morale, and it was much less of a surprise when they equalised 10 minutes later, through Yorke's header from Cole's clever cross. Between times, however, Keane had committed the offence that will cost him his place in the history of the European Cup final.
It was his own fault, although he spent several moment berating Jesper Blomqvist for the incident that led to the fateful yellow card. Blomqvist, playing with quiet intelligence in Ryan Giggs's place on the left wing, slid the ball across the centre circle, a pass intended for Keane but only narrowly evading Nicky Butt and Zidane. The Irishman could have steered the ball out towards David Beckham, but muffed his attempt to control it, instead allowing it to run past him. Zidane, thinking quickly, nipped round him to steal possession, but not quite quickly enough to prevent Keane from tripping him and preventing a dangerous break.
Keane's fate was in no way a replica of the shabby fraud that put Laurent Blanc out of the World Cup final. Neutrals can feel sympathy for Keane, but not real sorrow. The similar fate of Paul Scholes, booked for tackling Deschamps with both sets of studs showing, seemed marginally less justified, since the essence of the tackle was an attempt to win the ball.
Ferguson, who holds both players in particularly high esteem, remarked afterwards that they would be the first names on his team sheet for the FA Cup final, four days before the showdown in Barcelona. This is hardly good news for Newcastle United, who may feel the force of Keane's disappointment in particular.
United won Wednesday's match because they had more spirit than Juventus, and because they kept their shape far more effectively. At two goals down, and with the 58,000 home supporters already booking their tickets to Catalonia, Ferguson's players never wavered. They were not playing well, but they refused to panic. By maintaining their own tempo, and remembering their strengths, they grew into themselves and into the match, prompted by the unceasing and utterly unselfish exertions of Cole, who looks thoroughly at home in such surroundings and may have an important influence in Barcelona.
Cole has not had an easy time at United, but his refusal to learn the meaning of discouragement is matched by his subtle understanding of angles of attack. Yorke had a great deal to thank him for in Turin, and repaid the debt in the closing minutes by making the run which allowed his partner to pounce on the loose ball and score a well deserved goal of his own.
Juventus, on the other hand, fell victim to a major attack of hubris, their disintegration forcing Carlo Ancelotti to make a catastrophic half- time adjustment. By adding an extra attacker and withdrawing Zidane slightly, Ancelotti presented United with a far more familiar style of opposition, one which the visitors' defence was able to confront with greater confidence.
Zidane, whose display at Old Trafford had matched anything seen anywhere this season, came in for a mighty hammering in yesterday morning's newspapers, but the Italians had only themselves to blame for any deficiencies in his performance. Gianni Agnelli's careless insult at the beginning of the week may or may not have affected Zidane's competitive edge, but the country that invented the overheated transfer market can hardly complain when a player voices his intention to take advantage of the opportunities it offers. And Zidane was, in any case, far from the worst offender.
Where were Antonio Conte, the club captain, and Didier Deschamps, the captain of France, when the fight for survival was on?
Exempted from criticism would be the combative Edgar Davids, the tireless Angelo Di Livio, and most of all Filippo Inzaghi, a marvellously swift and agile predator. "I thought, I dreamed, that those two goals would be the most important of my life," the striker said afterwards. "Instead they turned into the most bitter."
As Ferguson looks ahead to Barcelona, there may be some comfort in the knowledge that the absence of Keane and Scholes will be balanced by the injuries that exclude two of Bayern's first-choice players, the Brazilian striker Giovane Elber and the French wing-back Bixente Lizarazu. And, with luck, United will have Giggs back in time for the final - a Giggs who, effectively denied exposure in the World Cup, must seize the best opportunity he will ever get to give the world a sustained exhibition of the immense talent that flared momentarily back to life a week ago.
But, most of all, the evidence of Wednesday night's amazing achievement in Turin points to two heartening conclusions. After a dozen years in the job, Alex Ferguson has created a team that is greater than the sum of its expensive and talented individuals. And, at long last, Manchester United have learnt what it takes to win back the trophy they hold most dear.
UNITED'S EUROPEAN GLORY NIGHTS
1965-66 Quarter-final second leg
Benfica 1 Man Utd 5
George Best was dubbed El Beatle after he scored twice in one of his greatest performances in a United shirt as Matt Busby's side humbled the mighty Benfica in front of their own disbelieving fans.
1967-68 Semi-final second leg
Real Madrid 3 Man Utd 3
United's European dream was in jeopardy when they trailed 3-1 at half-time and 3-2 on aggregate in the Bernabeu, only for Bill Foulkes to complete a great comeback with the equaliser and earn them a place in the final.
1967-68 Final, Wembley
Benfica 1 Man Utd 4 (aet)
Benfica had equalised to send the final into extra time only for George Best to find the energy from somewhere to weave his way through the bemused Portuguese defence and put United back on course for their most glorious moment to date.
1996-97 Quarter-final first leg
Man Utd 4 Porto 0
Ryan Giggs helped destroy Porto with a display reminiscent of George Best's destruction of Benfica 31 years earlier in one of the great European nights at Old Trafford.
1997-98 Group B game
Man Utd 3 Juventus 2
Ryan Giggs was once again the star of the show as United recovered from a first-minute goal from Alessandro Del Piero to beat arguably Europe's best side at Old Trafford.
1998-99 Quarter-final first leg
Man Utd 2 Inter 0
Alex Ferguson hailed David Beckham as the best crosser of the ball in Europe after he supplied the bullets for Dwight Yorke to shoot down Internazionale with two first-half goals.
1998-99 Semi-final second leg
Juventus 2 Man Utd 3
Manchester United produced one of the greatest fightbacks of all time as they came back from being 2-0 down after 10 minutes to win in Italy for the first time and end their 31-year wait to reach the Champions' Cup final.Reuse content