United's title bid was dramatically put back on track by Ryan Giggs' late winner in stoppage time at Carrow Road.
Paul Scholes had threatened to steal the headlines from Giggs on the Welshman's 900th appearance by heading home an early opener that, for so long, looked like being the only goal of the match. Norwich were not killed off and, instead, maintained a foothold in the game when Grant Holt equalised with only seven minutes remaining.
But Giggs had the final say in the dying seconds when tucking home an Ashley Young cross to cap a remarkable spell of pressure after Danny Welbeck looked to have twice passed up the opportunity to take the points.
Giggs flicked over from a Phil Jones cross with six minutes gone and, while that would have been a fairytale start, a goal was still forthcoming a minute later. A steady build-up did not appear to carry too much threat but there was a real sting in the tail when Nani whipped in a teasing cross from the right. Javier Hernandez and Welbeck were unable to get a touch but Scholes arrived on cue to give his nod of approval to the inviting centre.
A splendid move almost brought a second on 16 minutes when Nani and Hernandez ferried the ball to Welbeck but the striker's goalbound shot was expertly tipped away by Ruddy's fingertips with the keeper at full stretch. But Norwich retaliated, with David De Gea matching Ruddy's excellence with a vital block with his right boot to deny Anthony Pilkington, who beat Patrice Evra to advance onto a fine pass by Kyle Naughton.
Hernandez was unable to get any power on his shot after receiving a pass from Welbeck, with Ruddy saving comfortably, but De Gea was arguably busier than his opposite number in the first half. Pilkington's cross was met by a deft header by Holt but the Spanish keeper was equal to it,