Manchester United were toppled by a goal from former Old Trafford youth player Anthony Pilkington in a shock 1-0 defeat at Norwich City's Carrow Road - a result that leaves Premier League champions Manchester City back at the top of the standings.
Sir Alex Ferguson's side needed a win at Norwich to protect their two-point lead over City after their fierce rivals demolished Aston Villa 5-0 earlier in the day, but were undone by a moment of brilliance from Pilkington, who rose to loop a header beyond the visiting goalkeeper Anders Lindegaard from Javier Garrido's inviting cross on 60 minutes.
Without the injured Wayne Rooney, United huffed and puffed but could not find a way beyond an assured Norwich goalkeeper John Ruddy, who had the final say of the day when he dived to save an Anderson effort before smothering the ball as fellow United substitute Paul Scholes tried to force home the rebound.
In truth, United probably did not deserve more than a point from the contest after a fairly mediocre performance in which they never managed to truly pull Norwich's players out of position.
Norwich are six matches unbeaten since a 1-0 win over Arsenal at Carrow Road last month.
They won only their second of 11 Premier League meetings with Manchester United, and kept a third Premier League clean sheet in a row for the first time since 1994.
United's five-match winning run in the league, which began with a 3-0 win at Newcastle at the outset of last month, came to an end.
They can have few complaints after doing little of note in the first period. Robin Van Persie saw Ruddy palm away a shot on three minutes, but the visiting side would flatter to deceive for long spells afterwards.
Pilkington showed his menace when he drilled an effort wide from 20 yards out after being sent spinning clear by Wes Hoolahan, who was very much to the fore in the first period.
Ryan Giggs picked out Van Persie with a delightful pass on 38 minutes, but the Dutch forward failed to connect with the loose ball. It was a moment of rare danger as Norwich's well-organised defence continued to frustrate the visiting side.
United threw on Danny Welbeck for Javier Hernandez in the closing 20 minutes, but he saw a header deflect wide of goal as it became obvious a goal was not going to materialise with a series of crosses from Ashley Young.
Substitute Jonny Howson should have buried United when he raced clear a minute from time only to slam a shot wide while Ruddy was forced to show his agility to prevent Sebastien Bassong scoring an own goal with a header.
That would have handed the visitors a point they would have barely deserved.
MAN OF THE MATCH
Anthony Pilkington: Never stopped working and scored a brilliant winner for his side.
NORWICH: Ruddy 8; Garrido 7, Bassong 7, Turner 7, Whittaker 7; Pilkington 8, Johnson 7, Tettey 7, Snodgrass 7; Hoolahan 7; Holt 7. Subs: Howson 5, Morison 6, E. Bennett 6
MANCHESTER UNITED: Lindegaard 6; Rafael 5, Smalling 7, Ferdinand 5, Evra 6; Valencia 5, Giggs 6, Carrick 6, Young 6; Van Persie 6, Hernandez 5. Subs: Anderson 6, Scholes 6, Welbeck 6