Morten Gamst Pedersen's double earned Blackburn a shock win at Old Trafford as Manchester United were left to rue a catalogue of missed chances.
Pedersen gave Blackburn a first-half lead as his free-kick drifted straight into the net.
Ruud van Nistelrooy levelled for United when Wayne Rooney's shot proved too hot for Blackburn keeper Brad Friedel.
But an error by Paul Scholes gifted the ball to Michael Gray who set up Pedersen to slam home the winner.
In an attempt to emulate the two draws they got against United last season, Blackburn boss Mark Hughes opted for the defensive qualities offered by Pedersen over Brett Emerton.
But it was Pedersen who carved out the first chance, breaking on to Paul Dickov's pass to square the ball across goal where the Scottish striker's lunge just failed to make contact.
Rovers' gameplan might have been to swamp United in midfield, but there was still a good ebb and flow to the game.
United carved out a series of five chances in a seven-minute spell but failed to convert any of them and they needed Edwin Van der Sar's point-blank save from Dickov's header to keep them level as Blackburn again threatened on the break.
Rio Ferdinand found Craig Bellamy a constant handful
Van der Sar was extended again by David Bentley and it was no huge surprise when Blackburn took the lead on 33 minutes as Pedersen's free-kick from the right was missed by a clutch of players and swung into the net.
As United's frustration grew, Cristiano Ronaldo was lucky to escape with a yellow card as he appeared to shrug off the attentions of Gray with the use of an elbow.
United continued to waste chances and Van Nistelrooy somehow failed to make contact with Ronaldo's free-kick from a yard out.
That signalled an end to United boss Sir Alex Ferguson's patience and he introduced Rooney from the bench to try and salvage the situation.
Almost inevitably it paid dividends as Friedel was unable to hold onto his shot, and Van Nistelrooy was on the spot to snap up the loose ball for his sixth goal of the season.
But just as United prepared to hunt for the winner, Pedersen shocked them with a second goal.
Paul Scholes was caught in possession on the edge of his own box by Gray who fed Pedersen to slam the ball into the roof of the net from 12 yards.
Manchester United boss Sir Alex Ferguson:
"It was a bitter blow, and I am concerned about the gap to Chelsea.
"But I'm not as concerned about making sure we get back on track, and we know the crux of the problem.
"There were weaknesses in our defending which kept us on the edge, Blackburn capitalised on it and I can't deny them their victory."
Blackburn manager Mark Hughes:
"We came here with a game plan, there were areas we knew we could exploit and we had the players to do it.
"We expected pressure in the second half but we withstood everything and in the end they were just hitting long balls into the box.
"You have to be mentally and physically strong at Old Trafford, and we were."
Man Utd: Van der Sar, O'Shea (Bardsley 57), Ferdinand, Silvestre, Richardson, Fletcher (Rooney 55), Smith, Scholes, Ronaldo, van Nistelrooy, Park (Giggs 69).
Subs Not Used: Howard, Miller.
Goals: van Nistelrooy 67.
Blackburn: Friedel, Neill, Khizanishvili, Nelsen, Gray, Bentley (Emerton 75), Tugay (Mokoena 45), Savage, Pedersen, Bellamy, Dickov (Reid 63).
Subs Not Used: Kuqi, Enckelman.
Booked: Savage, Bentley, Bellamy.
Goals: Pedersen 33, 81.
Referee: P Dowd (Staffordshire).