Cristiano Ronaldo's hot streak continued on Saturday with two more goals in Manchester United's 3-2 victory over Reading at Old Trafford which put them six points clear in the Premier League.
The tricky Portuguese flyer has now scored 12 league goals this season, six of them coming in the last three games, and he is just just one behind Chelsea's Didier Drogba, whose 13th league goal of the season came in a costly 2-2 home draw with Fulham.
Arsenal slipped out of the top four, losing 1-0 in the mud at Sheffield United, where the hosts played the last 30 minutes with midfielder Phil Jagielka in goal.
United have 53 points from 21 games, Chelsea have 47 and Bolton Wanderers (39) are now third after a 3-2 home victory over Portsmouth. Liverpool are two points further adrift in fourth after winning 1-0 at Tottenham Hotspur.
On a day of torrential rain which resulted in one match being abandoned, the stormclouds are gathering over Stamford Bridge where Chelsea's grip on the title is slipping.
"Six points is not a drama, what is a drama is that we cannot defend," Chelsea manager Jose Mourinho told BBC Radio.
"In the past Chelsea win one zero, now every team feels that they can score against us."
The only good news for Mourinho on a day when it emerged that playmaker Joe Cole could miss the rest of the season with a broken foot, was John Terry warming up on the pitch just two days after having keyhole back surgery.
Drogba looked to have won it for Chelsea when he headed in Frank Lampard's cross but Carlos Bocanegra equalised late on to give Fulham a draw and take Chelsea's total of goals conceded in their last four league games to eight.
DEFLECTED SHOT
Fulham had taken the lead through Moritz Volz before Lampard's fierce shot was deflected in by Liam Rosenior.
Reading, who drew 2-2 with Chelsea on Tuesday, had not played at Old Trafford for 50 years but pushed the leaders all the way. Ole Gunnar Solskjaer gave United the lead but Ibrahima Sonko headed Reading level before halftime.
The second half belonged to Ronaldo who restored United's lead after Solskjaer hit the post before volleying his second. Leroy Lita pulled a goal back late on.
"It's been a very good day for us but we had to work very hard," United boss Alex Ferguson, who will be 65 on Sunday, told Sky Sports. "It was our worst defending of the season, I don't understand that.
"The rain was never ending and Reading made us play all the way to the end. In the second half it made a difference with Ryan Giggs coming on."
Arsenal trailed to Christian Nade's well-taken goal four minutes before halftime and Sheffield United hung on for a first league win over the Gunners since 1973 despite keeper Paddy Kenny going off injured and having to be replaced by Jagielka.
Nicolas Anelka's fifth goal in five games proved decisive for Bolton as they dislodged Arsenal from a Champions League spot, while Luis Garcia's strike was enough for Liverpool to end Tottenham's 12-match winning streak at home.
Everton's Victor Anichebe scored twice in a 3-0 victory over Newcastle United. Phil Neville was also on target with his first league goal for four years.
Bottom club Watford's home match against Wigan Athletic was abandoned early in the second half because of a waterlogged pitch with the score at 1-1.
Charlton Athletic boosted their survival hopes with a 2-1 home victory over Aston Villa, Bryan Hughes scoring in the last minute to seal a first win for new boss Alan Pardew.
West Ham United, the club who sacked Pardew earlier this month, were beaten 1-0 at home by Manchester City to remain just two points above Charlton in the bottom three.
Watford are on 11 points from 19 games, Charlton have 16 from 21 with West Ham are on 18. Middlesbrough, beaten 2-1 at Blackburn Rovers, have 21.