Six minutes later, Cleverley picked up a Rooney pass but there looked little danger to Harper's goal until he hooked a David Beckham-esque swirling drive past the keeper's despairing dive and into the top corner of the net. It was a moment of magic by the midfielder, who is looking more and more at home in the team.
De Gea bravely kept the hosts at bay, and took James Perch's studs in his thigh after the defender had already been booked, and Paul Scholes came on for Rooney in a bid to see out the final 10 minutes. Cabaye appeared to lose his cool after an off-the-ball clash with van Persie as things became somewhat heated in the closing stages with the Dutchman being withdrawn for Ryan Giggs as the clock ticked down.
Ba worked De Gea but much of the fire had long gone out of the hosts' attack, although not from their tackling. It was Scholes, however, who became the eighth player booked by Howard Webb after a foul on fellow substitute Shola Ameobi.
This was a stunning result for Sir Alex's side and sends out a warning to the rest of the Barclays Premier League - United are ready, willing and able to scrap for another title.