So before kick-off, it was fair to say that Derby County's resilient bunch had already enjoyed their day in the sunshine.
Gymnastic fantastic: Nani celebrates opening the scoring with a flying somersault
It did not stop them packing out Pride Park in the slight hope that a shaft of light may strike down on them a second time, following their Carling Cup triumph last month.
It soon became clear that there was little chance of that happening. This Manchester United
team have the scent of an unprecedented Grand Slam in their nostrils.
Golden oldie: Manchester United's Ryan Giggs battles for the ball with Derby's Nacer Barazite at Pride Park
Ferguson's side may have been slightly under-strength but it was still sufficient to darken Derby's bright new dawn under Nigel Clough. And then some.
Two goals before half-time - from Nani and Darron Gibson - broke the initial resistance. A Ronaldo header within minutes of the restart rendered the tie effectively over.
Despite Miles Addison reducing the deficit, there was still sufficient energy in the tank for Danny Welbeck to give another indication of his growing promise with a sweet, first-time strike.
Ramming into him: Cristiano Ronaldo and Robbie Savage square up to each other
What will please Ferguson, though, was the fact that he did not need to name a recognised striker, although it was difficult to tell that, such was the manner in which Ronaldo and Ryan Giggs occupied the roles.
'When we saw the teamsheet, we wondered what they would do up front,' said home midfielder Robbie Savage after the final whistle.
'In fact, we're still trying to work it out now.'
So good was the movement between the two front-runners and the wide men that it was easy to understand Savage's point. After all, he spent the majority of his time in a vain effort to chase those shadows.
Ronaldo, obviously, caught the eye. Such is his athleticism, fleetness of mind and feet that he remains the one player in world football even the most cynical fan would be happy to hand over their money to watch.
Wing wizard: The Portuguese tries a cheeky back heel at goal
But - and this is saying something - Giggs was better. He occupied positions for 90 minutes which left Derby's defenders indecisive.
They could not work out how to pick him up or, indeed, who was to pick him up.
A case in point was the opening goal. A move that worked its way along the Derby box eventually ended, via Giggs, at Nani's feet on the left-hand corner of the area. The Portuguese stepped inside and up a gear and unleashed a rocket of a shot from his right boot that flashed past Stephen Bywater before the home goalkeeper had time to dive.
Shortly before the interval came a talking point that would have caused greater controversy had the scoreline been closer. A ball was threaded into midfield, Giggs produced a magical flick and Ronaldo hared clear.
He finished with aplomb and his team-mates flocked to him in celebration. But some 10 or so seconds after the ball hit the net, assistant referee Paul Tierney raised his flag and referee Alan Wiley disallowed the goal.
Showing his frustration: Rio Ferdinand (centre) throws his hands in the air after referee Alan Wiley disallows a United goal
It transpired that the reason for the delay was that the assistant wanted confirmation Giggs had touched the ball as Ronaldo was then offside. Television replays showed that it was marginal at best. It would be heartening to write that the decision was greeted with a shrug of the shoulders on the visiting bench. Of course it was not.
UNSUNG HERO DARRON GIBSON (Man Utd)
The Derry-born midfielder, who prefers to play for the Republic rather than Northern Ireland, showed why he has come to the notice of Giovanni Trapattoni. Only 21, but he gave the sort of mature show you expect from United kids.
Ferguson was full in the face of fourth official Rob Styles although, for once, it was not without reason.
Moments before the break, the luck evened itself out. Ronaldo's free-kick clattered into the wall and bounced up into the air.
When it came down, Gibson smashed it into the corner. Rafael da Silva was standing in an offside position and jumped over the ball but the goal stood.
Three minutes after the interval, a Giggs corner was nodded home by Ronaldo, who celebrated legitimately, raising his arm up and down in quick succession to mimic the earlier decision.
HAVE YOUR SAY: HOW ARE YOUR FA CUP UNSUNG HEROES - Post your comments in the box below.
Derby day ruined: Rams keeper Jordan Stewart retrieves the ball from the net on a difficult afternoon for the Championship side
As during the second leg in the Carling Cup, Derby's players tried to maintain their enthusiasm and running. They were rewarded when Addison glanced home a Kris Commons cross to breathe life back into the contest.
But, marshalled by Rio Ferdinand, there was little likelihood of that happening again, although Ben Foster did produce a fine fingertip stop from Gary Teale.
In the end, it was Giggs and Fletcher who combined to leave Welbeck with the opportunity to open out his body and fire a curling shot into the corner of Bywater's net for the fourth.
DERBY COUNTY (4-4-2): Bywater 6; Connolly 6, Addison 7, Albrechtsen 5, Stewart 5; Teale 6, Savage 6 (Pearson 82min), Green 6, Barazite 5 (Sterjovski 62, 5); Commons 5, Hulse 6 (Porter 68, 6).
MANCHESTER UNITED (4-4-2): Foster 6; Rafael 6, Ferdinand 8, Evans 7 (O'Shea 55, 6), Evra 6; Park 6 (Welbeck 55, 7), Fletcher 7, Gibson 8, Nani 7; Ronaldo 8 (Possebon 73, 5), Giggs 9.
Man of the match: Ryan Giggs. Referee: Alan Wiley.
HAVE YOUR SAY: HOW ARE YOUR FA CUP UNSUNG HEROES - Post your comments in the box below. Derby 1 Manchester United 4: How the action unfolded
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