From Sir Alex Ferguson, there were no excuses. Sometimes there is no option but to admit the other side were better and, that evening in Rome, it was futile to argue otherwise. Manchester United had been outplayed, it was plain to see and for the losing manager the ordeal was so great, the jolt so shuddering, there have been times since when it has felt like he has wanted to shut it out of his life.

He has not, of course, and yet the oldest manager in the business has never properly offered his account of what happened that night – 27 May, 2009, the Champions League final and a 2-0 win for Barcelona that, for long spells, amounted to a master-class in the art of retaining possession.

At the start of the following season, Ferguson quickly made it clear he did not want, or expect, questions on the subject. For reasons only he properly knows, it has become one of his taboo subjects, broken over the past few weeks only because of the rematch that lies in wait at Wembley this weekend.

Even now, however, he is reluctant to go too deeply into what made it such a galling occasion. He has still not let on why he considers everything unravelled once Samuel Eto'o squeezed the opening goal past Edwin van der Sar. Or what he meant directly after the match when he said something had gone wrong with United's preparation: something he would not define but made clear he would put right if the sides ever met again.

What he will say is that Barcelona, this team of butterfly-beauty and quick, mesmerising, pass-them-to-death football, are an even more formidable unit than they were two years ago. "They've improved. They have more maturity about their team now. Winning that European Cup was a big step forward for them. This is a better side now."

Can the same be said of Manchester United? And was Xavi Hernández being genuine when he said this team of Ferguson's were markedly superior to that which crumpled so badly in the sweltering heat of the Stadio Olimpico?

The popular answer to both questions would have to be no considering United have lost one of the authentic superstars in Cristiano Ronaldo and no longer have Carlos Tevez even if, back then, the Argentinian was not always the player of strutting self-belief we see at Manchester City today. An alternative view is that Ronaldo demonstrated some of his more self-absorbed traits in Rome, shooting from the kind of distances and angles to concoct the sense among many observers he single-handedly wanted to turn Europe's premier club game into a one-man event.

Ferguson, for the record, disagrees, confiding once that Ronaldo was one of the few players not to warrant any blame. But he also believes there is enough hard evidence now to remove the sense that, without the Portuguese, they are a lesser team. United have just won the league by nine points. They qualified for this final without having conceded an away goal.

"All I can say is that all teams are different, the game evolves," he says. "I am well aware we have our critics, people who think we lack flair and don't play fantasy football, who believe we fall short of being a vintage side. As I once said to a pressman who observed that we were winning, but without firing on all cylinders, 'What do you want ... blood?'"

Those who are closest to Ferguson say that part of his strategy this time is to avoid talking up United's opponents too much. This is a side, he has told his players, who can be brilliant in thrilling, sporadic flashes, but who were only a miscued Nicklas Bendtner toe-poke from being eliminated against Arsenal in the last 16.

He has also subjected himself to several different versions of the match video from 2009 and the carelessness of his players can make him wince. Michael Carrick chose a bad night to have possibly his least distinguished game for the club. Nemanja Vidic was badly at fault for the first goal, standing off Eto'o, allowing him too much room to fire in his shot. For the second, Rio Ferdinand was flat-footed, Lionel Messi eluding him to score a rare headed goal.

In mitigation, it was Ferdinand's first game for more than three weeks. This has been another issue in United's preparations: Ferguson felt some of his players were not sharp enough in Rome. Anderson, who was so ineffective he was substituted at half-time, had not started a match for a fortnight; Park Ji-sung for two and a half weeks. This is why the team Ferguson selected against Blackpool on Sunday was stronger than had been anticipated.

Yet the video also tells Ferguson that in the first minute, Ronaldo hit a free-kick so well that Victor Valdés could only parry the shot and it needed a brilliant clearing tackle from Gerard Piqué to stop Park putting in the rebound. The enormity of that moment cannot be overstated. "But for what Gerard did," Thierry Henry, then of Barcelona, says, "it could have been a very different match."

Pep Guardiola's side had looked nervous until the opening goal. Passes went astray. There was one moment when Yaya Touré and Carles Puyol ran into one another. "We just couldn't settle," Henry admits. "There was a corner kick straight after [Ronaldo's shot], then a couple of crosses. You realise you're lucky not to be behind and you kind of forget who you are for a while. It's like when a great boxer gets knocked down. It doesn't mean he won't win the fight. But for the rest of the three minutes, until he hears the bell, he's going to struggle."

These moments have been lost in time now, inconsequential in the grand scheme of things once Barcelona started playing that rhythmic, fluent football that once had Ferguson talking of a team that "get you on the carousel and can leave you dizzy". Ferguson sat in the bowels of the stadium that night and there was unmistakeable sadness etched on his face. Maybe, he said, it would have made a difference if Darren Fletcher had not been suspended. "It wasn't really Messi who was the problem. It was Iniesta and Xavi. They can keep the ball all night long."

Ferdinand would later say that "not one of us played well". Wayne Rooney picked out Iniesta, describing him as the best player in the world. Ryan Giggs said: "At times Barcelona can make you look silly because they keep the ball so well." Then someone asked Ferguson whether, at the age of 67, he still had the desire to come back for more trophies. It was sweaty and airless, buzzing with mosquitoes, and it was here his emotions came to the surface. "I don't understand that question on a night like this," he snapped. "I don't like that stupid bloody question."

Two years on, he can be encouraged at least that United, even without Ronaldo, are in better shape. Fletcher is available this time. The squad is free of injury, and it speaks volumes that neither the club's player of the year, Nani, nor their leading scorer, Dimitar Berbatov, will probably get in the team.

"It's not just about Barcelona, it's about us, too – what's best for us and the best way of winning the match," Ferguson said. "Yes, I concede Barcelona are favourites in many people's eyes, and they have a super side. But I've always said that Manchester United like challenges. Don't write us off. You wouldn't want to do that."