'Stephan Andersen was nearly embarrassed by Rooney's alertness in the opening 30 seconds but proceeded to make two outstanding saves.
His countryman Peter Schmeichel would have been proud of the way Andersen clawed an Alan Smith shot from beneath the bar, but keepers are invariably remembered for their mistakes and it was a slip by the debutant that gave United a push start down the road to victory. Rooney's angled shot did take the slightest of deflections on its way through the goalmouth traffic but Andersen should not have allowed the ball to bounce off him. Paul Scholes punished the error in a blur.
Andersen does not lack for courage as two brave plunges at the feet of Scholes and Rooney proved, but he was desperately short of protection as United began to dismantle the Charlton defences with increasing ease. Shortly before half-time, the home team passed up several opportunities to clear their lines before Scholes rolled the ball back to Darren Fletcher to pick his spot.
Ferguson was soon able to spare Charlton further torment from Rooney and Scholes. But not before Smith had burst through a flimsy challenge from Talal El Karkouri to slide home his first goal since December, and Rooney had rounded off an exhibition of crisp instant passing with a flicked fourth.
Charlton's misery was compounded when substitute Chris Perry was dismissed for blocking Wes Brown's path to goal five minutes from the end.
United's fight to hurry Ferdinand into resolving his long-term future was accompanied by a faint undercurrent of boos at times from the raucous ranks of their supporters. "Rio, Rio, sign the deal," sang the fans. And much worse besides.
"We don't want to make a monster out of this thing," added Ferguson. "You can maybe push the players into these things and make it worse. He knows the fans want him to sign but if he's not sure he should take his time."