Manchester City raced five points clear in the league with a 2-0 win over Bolton Wanderers on Saturday while Chelsea's woes under Andre Villas-Boas continued after a 1-0 defeat at West Bromwich Albion.
With second-placed Manchester United visiting Tottenham Hotspur on Sunday, City stretched their lead as an own goal from Gretar Steinsson and a Mario Balotelli effort sealed their 19th successive home league victory.
Arsenal have not been in the title race all season but strengthened their claims for a top-four finish with Robin van Persie striking twice in a 2-1 triumph at Liverpool.
Van Persie's stoppage-time winner was his 31st goal of the season in all competitions and helped Arsenal move three points ahead of fifth-placed Chelsea who were beaten at West Brom by a late Gareth McAuley goal.
City have won all 14 home fixtures this season and are slowly edging towards their first top-flight title since 1968.
Roberto Mancini's team went in front after 23 minutes against Bolton when a shot by defender Gael Clichy took a big deflection off Steinsson.
Balotelli, back from a three-game suspension, then made the points safe after 69 minutes.
Chelsea are 20 points behind City after losing to West Brom in the Premier League for the first time.
Villas-Boas's side produced another lacklustre display which will again fuel media speculation about the Portuguese manager's future.
Frank Lampard wasted a glorious late chance for the visitors after McAuley's scrappy 82nd-minute goal had put West Brom in front.
NOT GOOD ENOUGH
"It was not good enough by Chelsea's standards," Villas-Boas told Sky Sports. "West Brom were far superior and we have to do much better."
While Chelsea, who have won just three of their last 12 league games, are faltering, London rivals Arsenal are flourishing.
A fourth consecutive league victory for Arsenal on Saturday means they are now only four points behind third-placed Tottenham.
Lethal Dutchman Van Persie volleyed the winner at Liverpool during eight minutes of stoppage time having earlier headed an equaliser after Liverpool had gone ahead with an own goal from defender Laurent Koscielny.
"It means a lot to score at Anfield," said Van Persie after netting at the ground for the first time.
"We're proud of the win but I don't think we deserved it if I'm honest. Liverpool played better but to nick it at the end is pleasing."
Liverpool, who won the League Cup on Sunday to ensure Europa League qualification, surrendered their unbeaten home league record and remain in seventh place, 10 points adrift of Arsenal with a game in hand.
Manager Kenny Dalglish was scratching his head wondering how his team had been beaten after they missed a first-half penalty and twice struck the woodwork through Luis Suarez and Dirk Kuyt.
Kuyt's spot kick and immediate follow up effort were both brilliantly saved by Polish keeper Wojciech Szczesny who was in inspired form throughout.
Martin Kelly also missed a glaring second-half opportunity for Liverpool.
"We had two men of the match today, one at the back and one at the front," said Arsenal manager Arsene Wenger referring to Szczesny and Van Persie.
Bottom of the table Wigan Athletic went down 2-0 at home to Swansea City as second from bottom Bolton lost at Manchester City.
Blackburn Rovers, one place above Bolton, drew 1-1 at home to Aston Villa while Queens Park Rangers moved up a place to 16th after a 1-1 draw with Everton.
Stoke City are eighth following a 1-0 home victory over Norwich City.
