Ferguson was present as Rooney, who celebrates his 28th birthday on Thursday, slalomed through the visitors' defence in the second minute of a thrilling European tie.
And while what proved to be the winning goal was turned into his own net by Inigo Martinez, the credit was all Rooney's as it was his shot that cannoned off a post and into the hapless defender.
Sat in the directors' box, Ferguson would surely have approved, even more so near the end when UEFA said Rooney had run over 10 kilometres - well above the team average, underlining exactly how much work he has been doing.
The Scot would have been less happy at the sight of his old team passing up so many chances to seal the win.
Even without Robin van Persie, who missed out with sore toes, United should have been clear long before the end.
Rooney had four more opportunities, and Shinji Kagawa - making a rare start - two. Phil Jones' header was turned away, Javier Hernandez had a goal disallowed for offside and Antonio Valencia struck a post.
So, if Antoine Griezmann or Alberto de la Bella had been slightly more accurate when they hit the woodwork, a nervous panic might have swept round the stadium that could even have silenced the 1500 inhabitants of the singing section, an experiment surely worth persevering with given the improved atmosphere.
The result means United now have seven points, just three short of the number Ferguson always felt guaranteed qualification for the last 16.
In this troubled start to his tenure, it is a welcome position for David Moyes to find himself in.
Around the same time as Ferguson was speaking in London on Tuesday, Moyes was sat at Old Trafford explaining why Rooney would not be affected by his former manager's words.
It was clear from the first whistle that the England man was intent on proving the truth of those words.
The only thing wrong with United's opener was that their number 10 was not credited with it.
After cutting in from the left wing and weaving his way past three defenders before planting his shot against a post, Rooney certainly deserved it.
Instead, the ball bounced back to Martinez, whose attempt to clear was so shockingly bad it ended up in his own goal. No mean feat considering he was on the edge of the six-yard box.
Not long after that, Rooney arrived with a perfectly timed run to meet Rafael's low cross.
This time his first time shot went straight at Claudio Bravo, who grabbed hold of it gratefully.
When Rooney set himself to meet Antonio Valencia's cross with an overhead kick, memories of that sensational Manchester derby winner fired into the same goal in February 2011 came flooding back.
Unfortunately for Rooney, he lashed it high into the spectators behind the goal.
Yet, as Southampton proved at the weekend, single-goal leads are not a comfortable position for Moyes' men to be in at present.
And, when Antoine Griezmann's free-kick crashed against a post just before half-time, it was a reminder of the potential for another nasty surprise.
The visitors began the second half brightly too and Jonny Evans hardly helped restore a sense of calm when he skidded a mis-hit clearance over his own crossbar.
A speculative effort from the touchline by De la Bella triggered the introduction of Chris Smalling for Rafael and another burst of attacking play by the hosts.
Rooney had a long-range effort saved and Jones' header was also turned away before Valencia burst into the box and smashed a shot against the far post.
Kagawa was well placed to snaffle the rebound but his effort lacked conviction.
The same accusation could be levelled against the Japan star when Valencia cut a cross into his path on United's next attack.
It needed a first-time finish. Instead, Kagawa tried to control and the chance was gone.
Rooney had a penalty claim waved away in the final minutes, after which Kagawa hit the side-netting.
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