United had a new Portuguese star to acclaim as Nani emerged the late matchwinner with a moment of brilliance to send the Red Devils top of the Premier League.
Filling Cristiano Ronaldo's boots was always going to be a tall order and Nani may never quite get there.
But even Ronaldo would have applauded the nerveless chip that broke Tottenham hearts 10 minutes from time after he had raced onto Federico Macheda's lay-off.
It put United back in front in a game they had to win, and when Giggs drilled home his second penalty, he transferred all the championship pressure onto Chelsea, who face Stoke at Stamford Bridge tomorrow.
As they had not lost to the Londoners since 1989 and Tottenham had not beaten a 'big-four' club on their travels for an incredible 66 games, a visit from Harry Redknapp's men is normally an occasion for United to relish.
However, in beating Arsenal and Chelsea in their previous two games Tottenham had not only blown the title race wide open again and re-established their own top-four credentials, they had also confirmed this particular Spurs vintage as the best in Ferguson's 23 years at Old Trafford.
Wayne Rooney's absence further strengthened anxiety in home ranks which the opening 45 minutes did little to dispel.
It took the hosts half an hour to manage their first effort on goal, when Antonio Valencia ignored the pleas for a pass from Dimitar Berbatov and went for goal himself, bringing a smart low save out of Heurelho Gomes.
Berbatov and Patrice Evra wasted decent opportunities shortly afterwards, although the hosts' best chance had come slightly earlier when Gareth Bale failed to cut out an Evra cross.
The loose ball was seized upon by Berbatov, upon whose shoulders so much could now rest.
Ledley King was there in a flash. His knees might prevent him from training but the defender's ability to anticipate danger is uncanny. Little wonder Harry Redknapp is urging Fabio Capello to offer the Tottenham captain a passport to the World Cup.
Not that the visitors were under a huge amount of pressure.
As a point would have been a decent return for Tottenham in their quest for that elusive Champions League place, Redknapp would have been far more pleased than old mate Ferguson with how the opening period panned out.
He would have been delirious if Roman Pavlyuchenko had found the net when Defoe provided a chested lay-off after Bentley lofted a cross into the home box. Instead, the Russian screwed his effort badly wide.
It was the start of a far more entertaining second period, which took its first significant twist 13 minutes after the re-start when Berbatov burst past Benoit Assou-Ekotto.
Although he appeared to have run down a cul-de-sac on the edge of the Spurs box, Berbatov remained aware of Evra's presence.
Assou-Ekotto knew the Frenchman was there too and when Berbatov supplied Evra with a impudent back-heel. The defender panicked, lunged in and sent his opponent flying.
There was more debate about who would take the spot-kick than whether it should be given.
Not once a scorer from the spot in his entire career, Giggs assumed the responsibility his role as captain demanded. It was not the most clinical of finishes but to Old Trafford's relief, he found the bottom right-hand corner of Gomes' goal.
In times gone by, that would have been it.
But with Antonio Valencia and Patrice Evra departing due to injury and ill-health respectively and Aaron Lennon arriving for the visitors, the pendulum swung back Tottenham's way.
Given the significance of the equaliser, Ferguson would have been fuming at how easily it was conceded.
King brushed aside Michael Carrick far too easily as he met Bale's corner with a firm header that Rafael would have cleared if he had remained by the post.
Instead he moved away and despite his acrobatics, the Brazilian was unable to keep it out.
At that point, Tottenham looked by far the more likely winners as Peter Crouch reinforced their attacking options.
But from virtually nowhere, United struck again 10 minutes from time as their own substitute Macheda collected Darren Fletcher's pass, then fed Nani.
There was not much space but he kept his cool and as Gomes raced out, he superbly chipped him.
The green and gold clad United supporters were still celebrating when Wilson Palacios clambered all over Nani four minutes from time, offering Giggs another spot-kick, which he buried into the opposite corner.