Manchester United regained top spot in the Premier League with a 2-1 victory over Bolton Wanderers at Old Trafford on Saturday as Liverpool's title bid suffered a potentially fatal blow.
Reigning champions United ended the day a point ahead of Chelsea, who started the weekend in first place but were beaten 2-1 by Aston Villa in Saturday's early kick-off.
Liverpool's quest for a first top-flight title since 1990 could now be over after a 1-0 loss away to Sunderland - their fourth league defeat in nine games, twice as many as they suffered in the whole of last season.
Tottenham remained third as former Portsmouth manager Harry Redknapp saw his current side hang on to beat the basement club 2-1 in a Fratton Park match where both sides finished a man down.
Spurs's north London rivals Arsenal moved into the top four with a 3-1 win at home to Birmingham.
Manchester United went ahead in the fifth minute when Bolton defender Zat Knight put through his own net after Patrice Evra's cross was flicked on by Michael Owen.
They doubled their lead when Antonio Valencia turned in Gary Neville's cross at the near post to score his first United goal since his pre-season move from Wigan.
Matthew Taylor's header 15 minutes from time gave Bolton hope.
United boss Sir Alex Ferguson said: "We had a lot of opportunities to finish the game and, when that happens, 2-0 leads are not particularly great. And when Bolton scored it was backs to the wall stuff and there was a bit of panic."
Chelsea manager Carlo Ancelotti was frustrated after setpiece errors cost his side dear at Villa Park.
They took a 15th minute lead when Didier Drogba's long-range shot bounced awkwardly in front of goalkeeper Brad Friedel.
But Villa levelled before the break when a poor header by England midfielder Frank Lampard allowed Richard Dunne to equalise from a corner.
Early in the second-half Villa again made Chelsea pay at a corner when James Collins rose highest to head the hosts back into the lead.
"We lost this game because there were two setplays from which Aston Villa scored two goals," said Ancelotti. "We need to be more focused in these situations."
Sunderland took the lead against Liverpool in extraordinary fashion at the Stadium of Light when striker Darren Bent's fifth minute shot hit a stray beachball on its way past Pepe Reina.
Liverpool, without injured stars Fernando Torres and Steven Gerrard, then survived seeing Bent glance a header just wide before the striker hit the post with an angled shot.
The match ended with tempers boiling over with rival managers Rafael Benitez and Steve Bruce exchanging angry words.
"We didn't play well enough to have bad luck," Benitez admitted. "We need to improve the performance of the team. They worked hard against a physical team but we have to play better."
Redknapp saw Spurs go ahead in the 29th minute when Niko Kranjcar - one of several former Portsmouth players in Spurs's line-up - crossed for Ledley King to head home.
Before the break they were 2-0 up when Pompey old boy Jermain Defoe turned in Jermaine Jenas's cross.
But in a twist former Spurs midfielder Kevin-Prince Boateng fired home for Pompey from close range just before the hour and shortly afterwards Tottenham were down to 10-men when Defoe was red-carded for lashing out at South Africa's Aaron Mokoena.
Goalkeeper Heurelho Gomes preserved Spurs's lead before Pompey's Michael Brown was sent-off just before the finish for a second yellow card.
"I felt people were disrespectful to the Portsmouth fans, talking about how they were going to behave," said Redknapp. "They were absolutely fantastic.
"We rode our luck and I was very disappointed with the way Jermain Defoe reacted."
At the Emirates, goals from Robin van Persie and Abou Diaby gave Arsenal an early lead before Lee Bowyer pulled one back for Birmingham.
Andrei Arshavin sealed Arsenal's victory six minutes from time.
In other games, Stoke beat West Ham 2-1 while Everton and Wolves drew 1-1.
James Beattie put Stoke ahead from the penalty-spot at the Britannia Stadium, but second-bottom West Ham levelled before the break when Matthew Upson headed in a corner.
Beattie restored Stoke's lead when Rob Green could only parry Ricardo Fuller's shot.
There was deadlock at Goodison Park until the 76th minute Kevin Doyle put Wolves in front.
But the visitors were denied a valuable victory when Diniyar Bilyaletdinov equalised two minutes from time before Wolves's Stefan Maierhofer was sent-off.
Blackburn Rovers play arch-rivals Burnley on Sunday when Manchester City face Wigan.