Harold Macmillan, asked what the biggest challenge is for any leader, famously replied: "Events, my dear boy, events." Macmillan, who oversaw the Profumo scandal, may have had something a little weightier in mind than a game-changing red card for a peripheral left-winger. But when it comes to football management, a business fraught even at the top end with events unforeseen and unforeseeable, the principal perhaps remains more or less the same.

Right up until Nani's sending off in the 56th minute, Manchester United and Real Madrid's last-16 Champions League tie had seemed to be heading in one increasingly distinct direction. At Old Trafford Ferguson had, in effect, out-José'd Mourinho. The redeployment of his front players, with Wayne Rooney replaced by the more mobile Danny Welbeck in the attacking-spoiler role, and the discipline of his central midfielders in denying Madrid counterattacking space had the air of a winning tactical plan. United were 2-1 up after more than two hours of the tie. Cristiano Ronaldo was increasingly trotting about with an air of waddling superstar fatalism. What could possibly go wrong?

That José Mourinho should emerge as victor in the battle of tactical wits says a great deal about the brutal syzygism of opposed footballing fates. Mourinho seized the moment with breathtaking decisiveness, standing down sub-in-waiting Karim Benzema and instead sending on Luka Modric to play through the heart of United's briefly listing midfield: Modric appears from the 60th minute of Uefa's post-match tactical analysis as a rogue blob in the lines between midfield and attack where there had been clear grass.

Before United could reorganise properly Madrid had scored two decisive away goals. By the end Ferguson had effectively "won" 165 minutes of this tie. Mourinho, brilliantly decisive with his opponent off balance, won the 15 that mattered, remaining entirely in the moment in the seconds after Nani's dismissal while Ferguson was standing on the touchline conducting the crowd to greater heights of indignation. When Mourinho says "Modric changed the match" it is clear what he really means: I changed the match.

Ferguson's non-appearance at his post-match press conference may have had something to do with the sense of having been picked off, expertly, in his own backyard. No doubt it had far more to do with the epic-scale anger and disappointment of exiting the Champions League when he will have harboured genuine hopes of a career-defining, and possibly ending, triumph at Wembley. With Madrid and, possibly, Barcelona out of the way only Bayern Munich would have presented opposition with a dangerous air of destiny about them.

As it is the next few months look fraught with possibility for both managers. Mourinho is almost certain to leave Real Madrid. Those who profess to know suggest his preferred destination is United, albeit perhaps with a potentially dicey stop-off at Chelsea along the way. Too much can be read into this: Mourinho may equally fancy the virgin pastures of the Paris Saint-Germain project with its accompanying souvenir league title and tooled-up outsider's shot at another Champions League. Either way he is three more victories from doing something that may never be done again, winning the Champions League with three different clubs in three different countries.

Plus, and perhaps just as significant in the short term, Mourinho managed to emerge from two days of intensive Champions League engagement without leaving a collective spume of violent outrage in his wake. As personal achievements go – and these things are relative – this was perhaps his most surprising gold star. And if there was something a little creepy about "nice" Mourinho here, the unnatural self-restraint, the self-consciously wonderful shows of respect for opposition fans and manager – there was a suspicion Mourinho's post-match TV interview ended ahead of time so he could rush off and find a locked door behind which to unload that three-day buildup of carminative personal bile – the likelihood is this was all part of a larger design.

Ferguson's career plans are a matter of some interest to a great many people, among them Mourinho, who at Old Trafford undoubtedly had the air of a man trying out his surroundings for size. The adverse reaction in Milan and Madrid against his often malevolent footballing personality has been overstated by the media: the travelling Madrid fans at Old Trafford chanted Mourinho's name regularly; Internazionale supporters made a point last month of celebrating his 50th birthday. But still here was a man – slightly gruesomely – on best behaviour, a houseguest with designs on something more.

For all the managed denials there is no doubt that Ferguson has for some time been actively contemplating the manner of his departure. Not that there is any sign of a withering of his powers. The decision to leave out Rooney was both imperious and, probably, correct. Welbeck was arguably United's best player while Nani, before his calamitous sending-off, provided some natural width on the left. Right up until the intervention of (dear boy) events, the plan was working.

There is no disgrace for Ferguson in being out-street-smarted by Mourinho and no doubt the public shows of affection between the two managers are born of genuine respect. Not least because of considerable similarities between the two: for all his hairdryer-schtick Ferguson's great skill in his late years has been the ability to tickle along the empowered modern superstar player, to turn his galvanising rage outwards instead of towards the media, other clubs, referees or any other handy stooge. Now: who does that sound like?

On Tuesday night Old Trafford seemed to swirl with possibilities – homecomings, extended farewell, long-range courtships. Mourinho emerged in understated triumph on and off the pitch, a step closer not only to European triumph but also to the Premier League job that looks the most natural fit for his own sense of grand personal destiny. Meanwhile for the first time it seemed possible at least one of Ferguson and Rooney may be out of Europe for the last time in a United shirt. Events: there's no accounting for them.