Chelsea suffered a shock 1-0 defeat at Crystal Palace while Manchester City were held to a 1-1 draw at Arsenal on Saturday, opening the door for Liverpool to go top of the Premier League in their home game on Sunday.
Jose Mourinho's Chelsea sank to their first defeat by Palace in 24 years after captain John Terry headed a Joel Ward cross into his own goal early in the second half amid suggestions the ball touched home defender Joe Ledley's hand on the way in.
The Stamford Bridge club stayed top on 69 points but could be overtaken by Liverpool who are a point behind going into their game in hand against Tottenham Hotspur at Anfield on Sunday.
Title favourites City are third on 67 points with two games in hand on Chelsea.
"Now I feel it's impossible to win the title," manager Mourinho told Sky Sports.
"We depend too much on other results. Two weekends ago we lost three points (to Aston Villa) and now it is too much about other results."
David Silva opened the scoring for City in the 18th minute before Mathieu Flamini equalised soon after the break to earn a draw for fourth-placed Arsenal who are on 64 points and retain outside title hopes.
Champions Manchester United ended a week of turmoil with a 4-1 win over Aston Villa, a double by England striker Wayne Rooney easing the pressure on manager David Moyes.
Palace's victory lifted them to fifth from bottom with 31 points, five clear of the relegation zone, and Selhurst Park was rocking at the end of the game with the joyous home fans belting out their 'Glad All Over' anthem.
Chelsea, who have six matches left, thrashed Arsenal 6-0 last weekend but gave a limp display against Tony Pulis' Palace who had failed to win in their previous five matches, scoring just once.
The Eagles grabbed the only goal when Terry headed the ball into his own net at the near post in the 52nd minute, leaving keeper Petr Cech stranded.
Eden Hazard had two opportunities to haul the visitors level but could not find a way past inspired keeper Julian Speroni.
Palace also had several chances to make the game safe with a series of lively counter attacks.
"We were threatening and played fantastically well," Pulis said. "We have seven games left to get the points we need and it's going to be tough."
City started brightly at the Emirates Stadium with Pablo Zabaleta and Jesus Navas causing problems down the right while Arsenal had a penalty appeal turned down at the other end when Zabaleta tripped Tomas Rosicky.
When the opening goal arrived it was little surprise that it was created and finished by the impressive Silva. He fed Edin Dzeko and when the striker's shot rebounded off the bar, the Spain playmaker slotted the ball home.
Flamini had a goal ruled out for offside but made no mistake second time round when Lukas Podolski found the Frenchman in the box and he scuffed his shot beyond the reach of keeper Joe Hart.
It was the first goal City had conceded in six matches and Flamini's first at the Emirates since 2008.
"I think it's a good point," said visiting manager Manuel Pellegrini. "We were maybe unlucky and we came to win.
"Before they scored we had a clear chance to make it 2-0. Arsenal had no clear chances - just the goal. Football is like that."
Seventh-placed Manchester United secured a welcome win over a spirited Villa, lifting some of the gloom surrounding Moyes' dismal first term in charge.
The Old Trafford crowd, many of whom booed an anti-Moyes banner that was flown over the ground as the match started, had further cause to grumble when Ashley Westwood put Villa a goal up in the 13th minute.
A double by Rooney, Juan Mata's first goal since leaving Chelsea and a late Javier Hernandez strike rounded off the win as United moved on to 54 points.
"I've been saying all the time I've been here, the crowd have been great ... because at times we haven't done as well as we'd like," said Moyes.
Goals by England trio Jay Rodriguez (2), Rickie Lambert and Adam Lallana helped Southampton rout a toothless Newcastle United 4-0.
Swansea City defeated Norwich City 3-0 while Peter Odemwingie notched the only goal in Stoke City's 1-0 triumph over Hull City.
Cardiff City fought back from going two down after nine minutes to draw 3-3 at fellow strugglers West Bromwich Albion.
The Welsh side rallied to level midway through the second half. They then conceded an injury-time goal to Thievy Bifouma before Mats Moller Daehli equalised with the last kick of the game.
Cardiff remained third from bottom in 18th spot, three points behind West Brom in 17th.