Was it really just that Rafa Benitez picked up Sir Alex Ferguson, put him in his pocket and administered the mother of all tactical tours-de-force?
Or could it also have been of some significance that Cristiano Ronaldo, the reigning world player of the year, was at times made to look like an inconsequential bit player beside his potential successor Fernando Torres?
Naturally, given all the previous, the Benitez-Ferguson issue had most play, and certainly it is true that the master of Anfield's deployment of both Torres and Steven Gerrard achieved a remarkable coup in the disintegration, for a day at least, of Nemanja Vidic.
But then we can go only so far with Benitez versus Ferguson, partly because the Liverpool manager, except for urging potential allies to attack the centre of United's defence with as much resource as they can muster for the rest of the season, largely resisted the urge to give back some of the recent ridicule aimed at him by the Old Trafford commander.
Their rival achievements and strengths are well enough estab
lished to over-ride any sweeping conclusions based on a single match between the teams, including the theory that Vidic has necessarily been diminished to the point that he is no longer one of his team's greatest strengths but suddenly a most glaring weakness.
Less speculative, surely, is the fact that Benitez has in Torres a brilliant centrepiece to all his hopes while Ferguson in Ronaldo does not. Certainly not for so much of a season which some expected to be nothing so much as
an extended coronation, and, on current evidence, in the foreseeable future.
No doubt there will cries that this harsh, especially when it is remembered Ronaldo headed United beautifully into a secure position against Internazionale and then nosed United into the lead against Liverpool with a perfectly placed penalty.
Yes, there is some danger of over-simplification, not least in the fact that if Torres received magnificent support from such as Steven Gerrard and Javier Mascherano, Ronaldo was not exactly surrounded by optimum performance from his team-mates, either against Internazionale or Liverpool. Indeed, if you wanted to define United despair at the end of a week of considerable dishevelment it was probably the sight of Michael Carrick, arguably their most influential player this season, being withdrawn from the challenge of breaking down a Liverpool defence which had allegedly become slow enough to be charged with loitering.
However, there can be no dispute about the fact that against Real Madrid and United, Torres was nothing less than luminous as he made Fabio Cannavaro, Italy's captain and the man of the 2006 World Cup, look both old and distraught, and then proceeded to undermine so severely the Player of the Year candidacy of Vedic. This was not so much a surge of form as confirmation of both superb talent and a burning competitive spirit.
Among his other woes, Ferguson could only have yearned for even hints of such commitment from his own superstar.
In a few weeks of fragile fitness Torres has become a fierce disciple of Benitez's cause. He wears a Liverpool heart on his sleeve, while, it it is difficult not to conclude, Ronaldo mostly sports one kind of advertisement or another for himself. Ferguson will no doubt bridle at this suggestion as much as the one that Benitez took him to the strategic and tactical cleaners, but the belief here is that it will be with less justification.
Whatever the undoubted cleverness of Benitez's work in Europe, where he twice left the messiah Jose Mourinho resorting to nothing more resourceful than long balls, he has never before been close to Ferguson's supreme quality of investing unbridled faith in his players.
This was most startling about Liverpool's eruption against both Real and United. Neither triumph was, whatever Benitez's most fervent admirers say, primarily about tactical pragmatism. They were the fruit of players operating at the peak of their powers. Torres and, to an almost equal extent, Gerrard played with a wonderful freedom and while Benitez can fairly claim that he has not often enough had both men available at the same time, there is also no great case for him, as there is for Ferguson, as a coach with an instinct for taking away the leash - at least until now.
For Ferguson the agony last week was the under-performance of players he has nurtured so relentlessly. While Torres flew, Ronaldo mostly fluttered.
Yes, there are some considerable points to be made in defence of Ronaldo. In every game he attracts small battalions of markers. His physical resilience is remarkable and, a cursory glance at their records tells you, far more so than the injury prone Spaniard. He remains, with the possible exception of Wayne Rooney, the United player most likely to produce a sublime and dramatic intervention, as we saw last week when the two of them combined to snuff out the rising hopes of Mourinho.
So where is the most pressing point of comparison? It is in the sense of Torres' commitment, of a determination to inflict all that he has for the benefit of the team.
Torres and Gerrard are at present emitting it from their very pores. Lionel Messi, along with blinding virtuosity, is doing the same on behalf of Barcelona. But Ronaldo is not and this, surely, gives Ferguson quite as much concern as the fact that Nemanja Vidic went missing for a day.
Ronaldo's absence, after all, has been rather more protracted - a fact illuminated by nothing so much as the passion of Fernando Torres.