Manchester United's slim hopes of retaining the premier league title disappeared in the most painful way possible on Sunday when they were beaten 4-1 at arch rivals Manchester City.
With 10 games left, United are now 12 points behind league leaders Arsenal and three behind second-placed Chelsea. Unbeaten Arsenal were 2-0 winners at Blackburn Rovers on Saturday while Chelsea triumphed 2-0 at Bolton Wanderers.
Liverpool and Newcastle United both lost ground in the chase for Champions League places with defeats at Southampton and Tottenham Hotspur respectively on Sunday while Aston Villa thrashed midlands rivals Wolverhampton Wanderers.
United's defeat, their worst in the league since 1999, means they have only the FA Cup, where they face Arsenal in the semifinals, as a realistic chance of silverware this season.
The result ended a traumatic week for United boss Alex Ferguson who revealed after their Champions League exit to Porto on Tuesday that he has had a heart pacemaker fitted.
"It was a terrible result for us, you can't mask that and we obviously want to do something about it," he told Sky Sports TV.
"The important thing is to try to get our form back in terms of winning matches and eradicating these silly errors we are making at the back," added the Scot, whose side have taken just two points from their last four league games.
City took a surprise lead with a close-range goal by Robbie Fowler after three minutes and doubled the lead when Jon Macken hooked the ball in from just inside the box after 32 minutes.
United pulled one back three minutes later when superb work by Ryan Giggs set up Paul Scholes to drive home his fourth goal in three games against City this season.
Giggs and Cristiano Ronaldo could have added more but City tightened up in the second half and got their third in the 73rd minute, a blunder by Mikael Silvestre offering Trevor Sinclair a chance he took with glee.
The hosts finished in style when Shaun Wright-Phillips lashed a spectacular shot into the roof of the net from wide on the right in stoppage time.
City manager Kevin Keegan was delighted with his team's third home league win this season and their second successive home derby success following their 3-1 victory in the last-ever clash at Maine Road last season.
"Everyone played a part, and none more so than the crowd," he said. "We've found it difficult to win here but I think they would swap all those disappointing days for what they've just seen out there."
Newcastle's hopes of climbing back into the top four were foiled at White Hart Lane when an 86th-minute own goal by Andy O'Brien gave Spurs a 1-0 win.
Liverpool slipped to eighth after unluckily going down 2-0 at Southampton in the home side's first game under new manager Paul Sturrock.
James Beattie put Saints ahead in the 51st minute and, after Michael Owen had a penalty saved by man of the match goalkeeper Antti Niemi, Kevin Phillips wrapped it up with a deflected 85th-minute shot.
Villa cruised to an easy 4-0 win at midlands rivals Wolves.
They took the lead after seven minutes through German midfielder Thomas Hitzlsperger and doubled it in the 18th minute with an Olof Mellberg header.
Another blunder by the home side six minutes later gifted Villa a third goal by Juan Pablo Angel and the Colombian got his second on the hour after Villa keeper Thomas Sorensen had saved an Ioan Ganea penalty.