Chelsea missed the chance to go seven points clear at the top of the Premier League when it was held to a 0-0 draw at Birmingham.
Chelsea created a handful of second-half chances but has now won just one of its past five Premier League matches, and that only with a late penalty against last-place Portsmouth.
The Blues are now five points clear of defending champion Manchester United, which could trim the deficit to two with victory at Hull - when Arsenal hosts Aston Villa.
“It is not a good result for us,” Chelsea coach Carlo Ancelotti said. “We are disappointed with the result but not for the performance of the team. We played well.
Birmingham tried to play the counterattack. It was a difficult game for us.”
Also, Manchester City beat Stoke 2-0 to close on Tottenham, which drew 0-0 at Fulham, while Liverpool beat 10-man Wolverhampton Wanderers 2-0 and West Ham beat Portsmouth 2-0 to climb out of the relegation zone.
Birmingham was unlucky not to be ahead at halftime against a Chelsea side featuring Daniel Sturridge in attack alongside Didier Drogba.
Birmingham striker Christian Benitez was called for a contentious offside when through on goal and then had a goal ruled out by a decision from the same linesman. The referee ruled out his close-range finish for offside, even though Drogba was playing everyone on by lying on the floor apparently injured.
Chelsea’s best effort came right at the end of the first half when central defender Alex smashed a 35-metre (yard) free kick against the post.
Chelsea coach Carlo Ancelotti eventually replaced Sturridge with Salomon Kalou in the 68th minute and the Ivory Coast striker wasted a pair of chances within two minutes.
He miskicked when totally unmarked and then had a shot saved by goalkeeper Joe Hart.
Nicolas Anelka is already out injured and Chelsea’s attacking options for Monday’s game against Fulham were further reduced when Florent Malouda was sent off for a second yellow card late on. The France international will be suspended.
But Ancelotti was given a boost when Ivory Coast allowed Drogba and Kalou to delay their departure to the African Cup of Nations until after Monday’s match.
Martin Petrov and Carlos Tevez scored first-half goals to give Roberto Mancini victory in his debut as Manchester City manager, Robinho was substituted after one of his worst performances for City.
City has 32 points, two fewer than Tottenham’s 34.
Mark Schwarzer earned Fulham a point with a late double save, stopping Peter Crouch’s long-range volley and blocking Jermaine Jenas’s effort on the rebound, but Tottenham’s Heurelho Gomes was the busier goalkeeper at Craven Cottage.
The Brazilian ‘keeper was forced into two stellar second-half stops by Bobby Zamora, one of three former Tottenham players in the Fulham line-up.
Gomes scrambled across goal in the 63rd to palm away Zamora’s downward header at the near post before making an even more acrobatic stop seven minutes later, keeping out another header with a diving save in mid-air.
“In terms of clear-cut goal chances I’d say we deserved to win that,” Fulham manager Roy Hodgson said. “Their goalkeeper made two or three very good saves and we scuffed one or two chances.”
Fulham’s United States international Clint Dempsey had earlier shot wide, hit a 25-metre (yard) free kick against the bar and almost set up a chance with a back-heel flick toward goal.
Damien Duff almost won it for Fulham when he shot wide just two minutes from the end.
Wolves held Liverpool with relative ease at Anfield until Stephen Ward was sent off in the 51st for a second yellow card when he pulled down midfielder Lucas Leiva.
Wolves replaced striker Kevin Doyle with leftback George Elokobi to beef up their defence but fell behind when Steven Gerrard headed a left-wing cross past goalkeeper Marcus Hahnemann.
Yossi Benayoun then made it 2-0 with a shot that deflected off midfielder Karl Henry, but last year’s runner-up is still five points behind the Champions League qualifying spots.
West Ham won for the first time in five games through a first-half penalty by Alessandro Diamante, awarded for a foul on midfielder Luis Jimenez by former West Ham player Hayden Mullins, and a late goal by Radoslav Kovac.
Hull and Bolton, which drew 1-1 at Burnley, join Portsmouth in the relegation zone as the Hammers moved up to 17th.
“It was a fantastic win, a massive one,” West Ham manager Gianfranco Zola said. “I rated this as a six-point game. It was so important for the table and for morale.”
Marouane Fellaini scored five minutes from the end to give Everton a 1-1 draw at Sunderland, which had led since the 17th through Darren Bent.