On his home turf at Old Trafford, Cristiano Ronaldo may look like the player he is supposed to be when the requirement is of the highest class, and the most natural-born commitment, and United may get more of a touch of the ball. Meanwhile, though, Sir Alex Ferguson is entitled to wonder whether the team on the verge of a Champions League and Premier League double have the decisive and defining quality of his boys of '99.
Though he would probably deny it with his dying breath, the Ferguson team who delivered the stunning treble in those last tumultuous minutes at the Nou Camp nine years ago did not distinguish themselves with anything like a masterful performance.
No, indeed, officials were pinning the colours of Bayern Munich on to the great trophy when United rallied and Fergie made his unforgettable, boyish run down the touchline. The celebration was, above all else, because his players performed, even without their best and most influential performers, Roy Keane and Paul Scholes, with that unique honesty of effort that had given their manager his unique status in the game.
The question now is whether the team who have to have on the biggest occasions Ronaldo so fitfully at their competitive heart, have the degree of resolve that carried United to the highest point of their modern history.
There was nothing wrong with United's determination at the Nou Camp this week, at least nothing that could not have been put right by more than occasional and fleeting possession of a ball that seemed to be owned by Deco and company.
One old pro, Liverpool's legendary striker Ian St John, was so surprised by Barça's monopoly of the ball, so much more than the normal disparity between the best Continental teams and those of the Premier League outside of Arsenal, that he mused: "I wonder if Barcelona had the decency afterwards to pop into the United dressing room to show them the ball and say, 'Here it is, lads, this is what we were playing with tonight'."
The worry is that but for the stalwart Scholes, who was on one of those surely dwindling best of the days that are left to him, United may just lack the midfield drive and authority that were embodied in the performance of Keane in Italy in the away semi-final leg against Juventus that carried the team, almost on their back, into the '99 final.
At Stadio delle Alpi, United were denied almost as much of the ball in the initial stages as they were this week. The difference was that none of Ronaldo, Michael Carrick or Park Ji Sung was able to impose himself enough to disturb the flow of Barcelona's game. It didn't help that Wayne Rooney, the one man with a touch and a vision to match those of Lionel Messi, found himself isolated and futile in too wide a position.
Of course, this can all be rectified next week at Old Trafford. A surge from Ronaldo that is not so much uninterrupted as stopped dead by the disappointment of a penalty miss (are we really sure we're looking at the new Georgie Best?), an eruption from Rooney, and the fears that Barça will rediscover enough bite to steal a decisive away goal, could be swept into the margins rather than their current position at the centre of United fears.
The new United pulled off a huge achievement in prising the Premier League away from Chelsea but they have yet to impress themselves as the sharpest on the trigger in the big one-off challenges. They came up short in last season's FA Cup final against a Chelsea scrabbling for some lost pride, having earlier virtually gone absent in the Champions League semi-final against Milan.
Ferguson must have died another thousand deaths when young Arsenal not so many months later, and in the immediate shadow of the Eduardo affair, played Milan off the San Siro field. No doubt, Ferguson yearned for such a performance this week. Instead, he got something rather short of being halfway between his most dismaying night in Europe and Arsenal's supreme performance on foreign soil.
He was given another chance to draw the the best out of his team, which we know is a considerable amount, while perhaps not pondering too long on what might have happened if Ronaldinho had been fit to play and more easily recognisable as the man who up until two years ago was not just a gift to Barça and Brazil but all of the game. Or if Samuel Eto'o or Thierry Henry had anything more than scraps of their old powers of sublimely timed penetration.
Wednesday's game was like watching not a fight but a bout of superior shadow boxing. Barcelona, it seemed, could have danced all night without laying a hand on United.
It will have to be different for both teams next week, but more different for United, who do not have Barça's incentive to try to keep possession of the ball all night, which on the evidence of the first leg cannot be put entirely beyond their powers.
Chelsea's Avram Grant inhabits the best of all semi-final worlds. Unlike United, his team don't have to score while playing at home and at Stamford Bridge they have the additional, and rather astonishing, encouragement that their opponents Liverpool have failed to do so on their last eight visits. Grant, who has already displayed at least a slightly histrionic tendency with his press conference mutiny last week, may already be fitting himself in a martyr's robes. Reviled not for his failures but the fact that he could not be mistaken for the absurdly revered Jose Mourinho, Grant is of course also, like Ferguson, a potential double winner and if he proves so, he can ride for ever on a sea of self-justification.
Chelsea did not light up the sky above Anfield this week but nor did they make a parody of sophisticated football while finding an escape hatch, as Mourinho's version did when twice subsiding under pressure in Champions League semi-finals at the same ground. Grant sat, once again glumly enough to bring fresh gloom to a Welsh funeral, without apparently once thinking of sending in a hulking central defender to try to get on the end of a series of balls humped into the box. That was the Special One's unswerving reaction to the deepest crisis.
Grant's demeanour may not be heroic, no more than the means by which he achieved his position at Chelsea, but who wants to bet against him now?