Publicly, Mourinho would think it abhorrent to have to impress a board of directors by knocking their team out of a competition.
His ego would not submit to a beauty parade.
United, though, would offer the smoothest return to the Premier League when his voyage across Italy and Spain is over.
Some senior figures at Old Trafford are against Mourinho as Ferguson's successor, citing his appetite for chaos and lack of interest in youth development. But it would be impossible to discount him were United to make a purely pragmatic, trophy-based decision about who to hire next.
Ferguson is not ceding power yet, but Mourinho will be the most eager candidate for the post. While many British managers scoffed at his braggadocio in 2004 ("I am the Special One"), Ferguson was impressed, recognising a kindred spirit.
It was not that Manchester United's manager arrived south from Aberdeen trailing sound bites or outrageous boasts; more that he understood the need to leave an imprint on those with the power, whether owners, players or pundits.
Timidity was never likely to impress United's supreme leader. Mutual respect was swiftly established as United squared up to Chelsea as the new No 1 challenger and Mourinho avoided political conflict with his older rival. That courtesy was never extended to Arsene Wenger or Rafael Benitez, with whom Mourinho was always eager to go into battle.
Ferguson says he likes Mourinho's "gravitas." But he will not like him trying to eject United from the Champions League.
Playing on a loop, of course, will be Mourinho's knee-slide when his Porto side equalised at Old Trafford in the round of 16 in 2004. The exuberance of his goal celebration that night might have made a permanent enemy of Ferguson. Instead, the old master saw something of his own youthful fervour in a coach with enamelled self-regard.
From the start of his three-year reign at Stamford Bridge, Mourinho drew a bead on United, looking to smother them with a strong midfield. His record by the end was two defeats in 10 meetings.
A 3-0 win against United in 2006 secured both Chelsea and Mourinho their second successive title.
The Real manager then was Manuel Pellegrini, a mere footnote now in the Bernabeu story. But Ronaldo's presence in Mourinho's side completes the triangle of old friendships and associations as United begin with a visit to Spain's capital on February 13.
United turned Ronaldo from a showboater to a superstar and Real now parade him as the embodiment of their tradition. With chin raised and knees pumping, he brings a suitably aristocratic hauteur to the white No 9 shirt.
Though United fans may find that threatening when he bears down on the ageing Rio Ferdinand, they are sure to appreciate the role he played in transforming United into Champions League winners again after the quiet years of the mid-2000s.
Vintners will also be on alert. Ferguson described the first wine Mourinho poured for him as "paintstripper."
The second was a £300 bottle of Portuguese red. Yesterday, Ferguson said on the club website: "Well, it's the tie of the round. It's a great opportunity for our fans to see Cristiano again and also for me to meet up with Jose again. I'll need to order some good wine."
Another vivid memory for both clubs is the standing ovation accorded to the Brazilian Ronaldo in 2003 after his hat-trick at Old Trafford. Ferdinand and Ryan Giggs both played in that game, which will be 10 years ago by the time of the rematch.
"It will be a thrilling experience for everyone. Manchester United are not only a great team, but a great organisation known around the world," said Emilio Butragueno, the Real legend.
"I know the coaches have a great relationship. We are very happy with him (Mourinho) and I hope he's going to lead the team to the Champions League. I would have liked to have played United later in the competition, but they won't be pleased either."
Already 13 points behind Barcelona in the league, Real are at least able to concentrate their energies on the manager's attempt to win the old European Cup with a third club (Porto and Inter were the others).
The expectation is that Mourinho will then wind his way back to England, where he seemed most at home amid the melodrama of our top league. Some in the Old Trafford politburo will continue to resist him, but his charisma in the short term is undeniable, as even Ferguson is happy to testify. (© Daily Telegraph, London)