Manchester United opened up a three-point lead at the top of the Premier League after beating Bolton Wanderers 2-0 on Wednesday.
The prolific Cristiano Ronaldo inspired the Reds to a fourth consecutive league victory with two classy first-half goals to take his tally for the season to 33.
In a rip-roaring London derby at White Hart Lane, Chelsea led three times against Tottenham Hotspur but were held 4-4. Joe Cole's double looked to have earned Chelsea the points before Robbie Keane struck with a superb 88th minute equaliser.
Victory would have put Chelsea level on points with Arsenal but they still trail the Gunners by two points and reigning champions United by five in a thrilling title race.
Ronaldo was captain for the night at Old Trafford and the Portuguese winger repaid manager Alex Ferguson's faith with a masterful display to see off struggling Bolton.
He crashed in his first after nine minutes following a corner and tormented Bolton again after 20 with another swerving free kick to add to his collection.
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His double means he has now surpassed the 32 goals scored by George Best in the 1967-68 season, the highest season's tally for a United winger.
Bolton did have an effort ruled out after the break but a fifth consecutive league defeat leaves them mired in the relegation zone.
Chelsea were left kicking themselves after squandering two points at Spurs, having led 3-1 with 15 minutes to go.
Didier Drogba gave the Blues the lead with a third-minute header only for defender Jonathan Woodgate, who scored the goal that gave Tottenham a memorable League Cup victory over Chelsea last month, to equalise after 10 minutes.
Michael Essien restored Chelsea's lead after being played in by Cole and Cole made it 3-1 after 52 minutes when he shrugged off a weak challenge by Pascal Chimbonda.
Dimitar Berbatov headed Spurs back into contention and substitute Tom Huddlestone made it 3-3 with a thumping shot through a crowd.
Cole pounced again to shoot high past keeper Paul Robinson but in a barnstorming finish Keane curled an unstoppable shot past Carlo Cudicini. Berbatov almost won it for Spurs in stoppage time but Cudicini somehow parried his close-range shot.
