The goal prompted Sir Alex Ferguson to introduce Paul Scholes and Danny Welbeck in place of Chicharito and Valencia, and Welbeck came close to levelling when his header drifted just past Ruddy's upright.
United's general play improved under the dawning realisation of the situation's gravity, but Norwich's resolve redoubled with every passing moment. Two yellow and green-clad banks of bodies steadfastly protected Ruddy, crucially keeping calm and sticking to their task under the mounting pressure.
Norwich passed up a glorious chance to double the margin of victory when Jonny Howson dragged a glaring chance wide, and were indebted to Ruddy's injury-time heroics as he tipped over Sebastien Bassong's errant header, then clutched substitute Anderson's low effort under heavy pressure from Scholes.
Having produced up an inordinate number of rousing late comebacks already this season, United finally returned to the well to find it empty.