Queiroz's acute appreciation of defensive systems was widely credited as the factor which helped United to prise back the league title from Arsenal in 2003. It led to him being poached by Real Madrid that summer and Arsenal duly regained their ascendancy.

But his return to United as assistant manager, after a disastrous season at the Bernabeu, presaged the abandonment of the 4-4-2 system which won the European Cup in 1999 in favour of a cagey and much derided 4-2-3-1 set-up which, even with Ruud van Nistelrooy as the solitary attacker, went against the very grain of United's famed spirit of adventure. "If we need to defend with 10 players behind the ball we are going to do that," Queiroz said at the time – and United fans loathed him for it.

All that seems a short lifetime ago. The 4-2-3-1 formation earns only occasional outings for United, and the man who will succeed Luiz Felipe Scolari in the Portugal job is credited with delivering the qualities which took United to the Double in May. Key among them were a defensive resilience which saw nine fewer league goals conceded than in the 2002-03 season and the blossoming fruits of his continental football knowledge and contact network, with one of Old Trafford's most unexpected immediate hits – Anderson – to go along with Cristiano Ronaldo and the relatively unproven Nani. The new stars were no more than Sir Alex Ferguson anticipated when he sought out Queiroz in 2000. "[I] needed someone ... who could speak in various languages, had a European culture and was able to bridge the different nationalities," Ferguson later observed.

Ferguson has spoken more recently of the way Queiroz, who was born in Mozambique but spent his football career in Portugal, had also introduced legions of dieticians and fitness coaches. The United manager presents himself as something of a Luddite on such matters and values the introduction to new ways. At times, the assistant manager has seemed to be joint manager.

The 55-year-old has not quite gone yet. A planned meeting at the Uefa HQ in Nyon yesterday between United's chief executive, David Gill, and the FPF president, Gilberto Madail, did not take place because Madail was called away. But the compensation agreement which the two men were to discuss should be forthcoming and Portuguese sources believe today is "D-day."

That leaves United with the unenviable position of attempting to fill Queiroz's shoes, five weeks away from the start of a season which they enter under a cloud of Cristiano Ronaldo's creating. Ferguson has been instrumental in drawing his alumni into the heart of his back-room team of late in a Bayern Munich model – Ole Gunnar Solskjaer will run the reserves next season, with Ryan Giggs and Paul Scholes likely to be offered coaching roles – which is why the current academy director Brian McClair and first-team coach Mike Phelan feature highly among the contenders. Bryan Robson, newly restored to Old Trafford as ambassador, would be an intriguing possibility.

Yet Ferguson will be aware that the value of hiring someone with a knowledge of Europe and its languages is even greater now than it was when he made it a prerequisite in 2000. Eric Cantona, about whom odds of 40-1 were being offered yesterday, is surely out of the question – a romantic Ferguson is not. But Cantona's countryman Laurent Blanc, the former United defender and current FC Bordeaux manager does looks a contender.

An equally aspiring young Portuguese manager seems harder to find now that Carlos Carvalhal – the "young Mourinho" as he is known in Portugal– recently left Setubal for Greek side Asteras Tripolis. A discovery from another of Europe's technically proficient nations – the Netherlands or Spain – cannot be ruled out for a job in which the rewards of success are huge but the responsibilities are formidable.

Red Replacements? Potential No 2s for United

Brian McClair

Highly intelligent United Academy director, with strong theories on youth development. Ferguson recently indicated he increasingly sees young signings as the future.

Ricky Sbragia

A journeyman player, the Scot built up successful United reserve side from 2002, nurturing talents of Kieran Richardson and Darren Fletcher before Bolton made him first-team coach in 2005.

Laurent Blanc

"Larry White", as United fans affectionately know their former defender, was a revelation in taking Bordeaux to second place finish in Ligue 1 last season.

Mike Phelan

United's first-team coach since Steve McClaren's departure to Middlesbrough and ambitious – about to embark on his Uefa Pro Licence.

Carlos Carvalhal

The "young Mourinho" has already pitched his tent in Greece, but his remarkable season at Setubal took them to the semi-final of the Portuguese Cup and Uefa Cup qualification.