Manchester United's hopes of retaining the Premier League title suffered a major blow as the champions were held to a 0-0 draw by Blackburn on Sunday.
Sir Alex Ferguson's side would have moved one point ahead of Chelsea with a win at Ewood Park but, with England forward Wayne Rooney sidelined through injury, they were unable to prise open Blackburn's stubborn defence.
The result left second placed United a point behind leaders Chelsea and the gap will increase to four points if the Blues win their game in hand at home to Bolton on Tuesday.
After bowing out of the Champions League against Bayern Munich in midweek, this was another significant setback for United, whose best chances were wasted by Antonio Valencia and Dimitar Berbatov.
"The title is slipping away when you don't get a result in a game like this," Ferguson said. "We are now a point behind Chelsea and they have a game in hand which would take it to four points. It's a big gap."
Elsewhere, Manchester City moved a step closer to qualifying for the Champions League with a 5-1 demolition of Birmingham at Eastlands. Roberto Mancini's fourth placed side are now four points clear of fifth placed Tottenham, although the north Londoners have a game in hand against title contenders Arsenal on Wednesday.
City took the lead in the 38th minute when Carlos Tevez struck from the penalty spot after Scott Dann fouled Emmanuel Adebayor. It was Tevez's 19th goal in his last 18 league games and City increased their lead two minutes later as Nedum Onuoha headed in Adam Johnson's cross.
"It's important we continue to improve in the next five games because we have five difficult matches," Mancini said. "It's probably between us and Tottenham, but I don't know because Liverpool have a very good squad. I must think only about our games."
Birmingham reduced the deficit through Cameron Jerome's 42nd minute header but Adebayor put City back in control with a tap-in that completed a crazy spell of four goals in five minutes. Onuoha struck again with a solo effort in the 74th minute before Adebayor fired home in the 88th minute to confirm City's third successive victory.
Reds slouch to scoreless draw
City's win was bad news for Liverpool, who look certain to miss out on a top-four finish after being held to a 0-0 draw by Fulham at Anfield.
Rafael Benitez's side were without star striker Fernando Torres due to a knee injury and his absence was crucial as the Reds failed to break down their fellow Europa League semi-finalists. Liverpool are six points behind City and have played a game more than Mancini's men.
"I'm a little bit disappointed. The fourth position is a little bit far away," Benitez said. "It depends on two or three other teams. The difference is maybe too much now."
Wolves edged closer to Premier League survival after grinding out a dour 0-0 draw against Stoke at Molineux. Mick McCarthy's team are six points clear of the relegation zone with four matches left to play and look set to beat the drop in their first season up from the Championship.