The Portuguese is not a man of regrets but how different might the landscape be if he had succeeded Sir Alex Ferguson?

On Sunday, a little before four o’clock, José Mourinho will leave the tunnel at Old Trafford and walk along the front of the South Stand.

He will see ahead of him the touchline along which he sprinted and slid in 2004 after his Porto side had beaten Manchester United in the Champions League with a late goal. And before the halfway line he will turn right, and take his place in the away dug-out. Given he is not a man who seems particularly to regret, he may not even cast a glance to the bench 15 yards in front of him and wonder what might have been but there is another reality, not that far removed from this one, in which he would have been sitting in the home dug-out.

In March 2013 Mourinho’s Real Madrid beat Manchester United in the quarter-final of the Champions League. It turned out to be Sir Alex Ferguson’s final European game as a manager, his awareness of which perhaps explained the extreme nature of his fury at the red card shown – extremely harshly – to Nani.

Ferguson was not the only one with the sense that night of an era ending. Mourinho also seemed aware that the United job would soon be falling vacant and to be positioning himself for it. In the build-up to the game he had massaged egos all round, talking about what a great club United was. Afterwards he insisted that “the best team lost. We didn’t deserve to win but football is like this.” It was as though there was a conscious effort to ingratiate himself with United fans and officials, to show he was capable of diplomacy.

That does not necessarily mean that, as the El País journalist Diego Torres claimed in his controversial book on Mourinho’s time at Real Madrid, Mourinho sobbed when he found out David Moyes had been named as Ferguson’s successor, but he was clearly extremely interested in succeeding Ferguson. Mourinho denied Torres’s version of events which describes him in the Sheraton Mirasierra hotel constantly on the phone to his agents, Gestifute, in the two days before Moyes’ appointment, as the realisation slowly dawned that he would not be getting the job.

He subsequently said that he would have turned down any other offer once it became clear he could return to Chelsea.

Whatever Mourinho would have done, United did not approach him, despite the fact that he was clearly going to be available and that, in terms of trophies won, he was the outstanding candidate. Ferguson had no doubt as to his talents: “José’s managerial ability became the biggest obstacle to our rebuilding,” he wrote in his autobiography of 2005. He considered him “exceptionally good with players … meticulous in his planning”.

According to Torres, Mourinho felt “betrayed” that Ferguson had apparently backed Moyes over him – although Ferguson’s updated autobiography, which came out this week, denies he was influential in selecting his own successor. Torres also suggests Mourinho was haunted by memories of an interview Bobby Charlton had given in which he said that a United manager would never have poked an opposing coach in the eye as Mourinho did to Tito Vilanova in 2011. It also seems that there was a suspicion around Old Trafford about Mourinho’s love of playing political games, something that characterised both the end of his first spell at Chelsea and the final months of his Real Madrid career.

So perhaps United were never going to appoint Mourinho. Even Madrid, it appeared, turned to him only in extremis, when the need to topple Pep Guardiola’s Barcelona was so pressing that the club was prepared to tolerate the more Machiavellian aspects of Mourinho’s way of doing things.

Style off the pitch is probably something of more concern to directors than fans but United on the pitch would have changed had Mourinho taken charge. Ferguson, in his autobiography, makes specific reference to fans at the Bernabéu watching a string of 1-0 wins and wondering if they might prefer some 5-4s. The specifics might not quite tally with the reality – in his three years at Real Madrid, Mourinho won only two home league games 1-0, both in his first season – but the general point is both understandable and transferable to Old Trafford.

Mourinho’s brand of football is distinctive in the modern age in being largely reactive: against better sides, his preferred method is to sit his side deep and attack on the counter, as Chelsea did with devastating effect against Manchester City and Liverpool last season.

Talk of clubs having a defined style that somehow endures no matter the players and the manager is often self-romanticising nonsense but there is a perception that United play cavalier football with wingers. Mourinho would never have had any truck with that.

Would that have mattered? Probably not. In football, results have a tendency to outweigh everything else. And besides, to think of Ferguson’s first great United is to think of Andrei Kanchelskis and Ryan Giggs marauding forward as Arjen Robben and Damien Duff did or as Eden Hazard and Willian can – phases of play usually established by a rapid transition after possession has been regained. That is not to say Ferguson’s style and Mourinho’s are the same but that in one attacking element they share a similarity.

Would the world have turned out particularly differently had Mourinho rather than Moyes succeeded Ferguson? Well, Chelsea would almost certainly not be five points clear at the top of the table and Juan Mata would probably still be playing for them. There would, at the very least, have been a greater sense of purpose about United last season, less sense of the shadow of Ferguson hanging over the squad.

They would probably have signed Nemanja Matic, Willian (or a similarly direct winger) and at least one central defender. Ángel di María, having played under Mourinho at Madrid and being very much his type of player, might still have arrived but there would not have been the binge of last summer. Given Mourinho always wins domestic titles in his second season, United may well have been on the way to becoming champions now. They would certainly have a better defensive record.

Time, though may deem the Moyes interregnum to have been a necessary break between two big personalities, as a palate-cleansing sorbet. It rather depends what happens next year, when Louis van Gaal is in his second season at Manchester United and has had time to instil his own philosophy.