Yet perhaps the real key to their surge is the influence of their Irish skipper Roy Keane, who is not only the heartbeat of the side but the cerebral inspiration as well.
This performance under-lined his real quality. He is a Pimpernel of a player, appearing when you least expect him, caressing the ball and cajoling his colleagues, encouraging one minute and berating the next. A leader of real stature.
United had to work hard. Southampton have enjoyed a resuscitation under Gordon Strachan. Their fitness is improved and they closed down United superbly in the final half-hour of the first half.
They harry, chase and play it simple, getting the ball forward to the strikers. The loss with a dislocated ankle of James Beattie, who had headed Saints into a third-minute lead, was critical.
Beattie was missed even though the debut -making Agustin Delgado - hero of Ecuador's World Cup qualification - made an able deputy, hitting the woodwork and forcing an astounding save from Fabien Barthez.
His goal was taken with a minimum of fuss, thanks to a stunning header from Jason Dodd's centre with Laurent Blanc once again failing to make a clean jump.
There was no time to build on the goal, however, for within five minutes Scholes had slotted the perfect ball for Van Nistelrooy to sprint on with confidence, beating Paul Jones at his near post.
Saints now enjoyed their most effective passage of play. Delgado headed Anders Svensson's centre against the far upright, then laid on a chance which the speedy Marian Pahars drove against the top of the bar.
Those kinds of opportunities need to be taken against United, as was demonstrated a minute from half- time when Fabrice Fernandes pulled down Scholes in ideal David Beckham territory.
From an almost identical position to the kick with which he put England into the World Cup Finals against Greece at Old Trafford, Beckham placed his delivery around the defensive wall and into the left-hand corner.
United now had control. Beckham's centre was headed against an upright by Ole Gunnar Solskjaer. It proved to be no more than a target tester for the Norwegian. When Van Nistelrooy dribbled across the edge of the Saints area, Solskjaer was waiting for the pass which he angled across Jones and into the corner.
Shoulders now slumped in the Saints side as United played keep-ball and although Delgado forced Barthez into a remarkable save nine minutes from time, United were already preparing to sit on their throne.
