1. The way United lost to Real Madrid is likely to strengthen Sir Alex Ferguson's determination to remain at the helm
Because Ferguson can – and almost certainly will - rationalise that his side lost to a freak event at Old Trafford on Tuesday night, rather than to a better team.
Against considerable odds and despite the "cartoon cavalcade" defence the manager was so exasperated about in early December, this new generation of players has demonstrated in the past month that they are perfectly capable of matching the European elite. Ferguson admitted that he wasn't entirely certain they were, on the eve of the first leg in the Bernabeu. "This will be the acid test," he said, and there seemed to be a laugh from him when someone talked about winning the European Cup. "Us?" he asked. United's vulnerability to the aerial ball in the first half of the season made you fear what terrors the Bernabeu might inflict on a side who were cut down at Norwich and Tottenham. They have more than coped.
They should – and could – have won the tie. If Robin van Persie had only pounced on his gilt-edged late chance in the Bernabeu, rather than fire it into the ground, taking the pace from the ball and allowing Diego Lopez to save, the course of the tie would have been different – and profligacy has certainly been United's cardinal sin over the 180 minutes.
Even with the tie balanced so precariously on Tuesday, they got their tactics right. They had nullified the Spanish threat and Cristiano Ronaldo when Cuneyt Cakir, the Turkish referee, intervened. Some of the young players Ferguson has watched carrying out his instructions to perfection across both games – Danny Welbeck, Phil Jones and Tom Cleverley foremost among them – will only reinforce his messianic belief that teams must be grown organically, and not simply bought. Yes, United still look short of a creative nexus in their midfield. Many Manchester United fans have argued with this correspondent's view that Rafael da Silva still does not possess the full defensive armoury in this, his breakthrough season. He had lost Ronaldo when he scored Tuesday's winner. But the broader picture is more positive.
Ferguson will have seen with his own eyes that the final United team to be shaped by him is a force in Europe, and without Cakir's intrusion might even have conquered it in May. The intrusion is just football, of course. Games at this stage of the season can so often turn on the unpredictable and unexpected.
No one knows what Ferguson's precise thoughts on retirement are and any discussion of them is guesswork. But the manager's finger-pointing and rabble-rousing on Tuesday reveal a man with heart for at least one more tilt at the trophy. It is a chance which has been bestowed upon him by these young players.
2. Wayne Rooney playing for Manchester City is no longer such an unimaginable prospect
Rooney's omission from one of United's half dozen biggest games of the past decade will have an impact on the renewal of the contract, worth £250,000 a week, which United were so desperate to sign Rooney up to, with Manchester City circling three years ago. After he had signed on the dotted line, Rooney declared: "Believe me if I had gone [somewhere else] it wouldn't have been in England." But United would not find a £40m bid from Manchester City as unthinkable now because he is simply not a £40m player.
Unitedy would remove £12m a year from their wage bill and Rooney may also find the wages he wants across Manchester. Would City be willing to pay them? Already one striker down, after Mario Balotelli's departure to Milan, they may also see Carlos Tevez depart this summer with one year left on his deal and no intention to renew. Roberto Mancini may not be in situ beyond the summer either but when Rooney was struggling to agree terms with United in 2010, the Italian expressed his appreciation. Where else? Europe is a possibility, though Rooney's representatives have not responded to suggestions about Paris Saint-Germain.
3. Ryan Giggs has demonstrated that mental energy is as important as physical fitness
His performance on Tuesday night defied any kind of logic. The player who was outsprinting Ronaldo at one stage and searing around the Old Trafford turf did not resemble the individual who has looked on a number of occasions in the past 18 months as if his days had come to an end. That is the kind of physical output that a surge in mental energy can deliver you.
4. Real Madrid prove that playing with 10 men is not as difficult as United made it look
Their manager Jose Mourinho declared this to be the case in his post-match press conference. "In history there are many examples of the team with 10 men holding out" – and a good example came when it took almost five minutes to get Kaka on the field after Angel di Maria was injured in the first half. Madrid maintained almost permanent possession, while when United went down to 10 men they dropped deep and allowed Madrid at them. Real also adjusted rapidly to their numerical advantage, turning the entire tie on its head before United sorted themselves out.
5. Player of the Year? Robin van Persie has his work cut out
Someone joked on Tuesday night that former Arsenal players are used to the season being over by February and though there are extenuating circumstances with Van Persie, who has been carrying a slight hamstring strain in recent weeks, the 15th-minute opportunity he could not make a full connection with at Old Trafford was one of a number of misses across both legs against Real Madrid.
His impact at United has been extraordinary in his first season but he has scored only once in eight games since striking at White Hart Lane in January.