United win thrilling clash
Manchester United claimed a record-equalling 18th successive home win to march two points clear at the Premier League summit with a 3-1 victory at Old Trafford.
First-half goals from Chris Smalling, Nani and Wayne Rooney - his ninth of the season - proved enough for the hosts.
However, Rooney also had a 'Moscow moment' missing a second-half penalty, slipping as he went to strike it, Fernando Torres scored only his second Chelsea goal, then unbelievably fired wide of a completely empty net after rounding David de Gea.
De Gea had already repelled a marginally less glaring chance for Ramires and in stoppage time, Dimitar Berbatov was denied by Cole, whose earlier poor challenge on Javier Hernandez had led the Mexican to hobble off in considerable pain.
It all ended with United matching an achievement from the 1904/05 season, when they were a Second Division club.
Correctly, Ferguson observed this was United's toughest test to date.
The same could also be said of Villas-Boas' Chelsea though. And they came up short.
Chelsea did carve out a succession of opportunities that at one stage turned the game into a personal contest between the Blues and De Gea.
The save that prevented Ramires prodding into an open goal was the best, drawing applause from Peter Schmeichel in the directors' box, and he knows a thing or two about the pressure of keeping net at Old Trafford.
In truth, Chelsea should have scored that one. Torres did his bit, rolling the ball across the box. A better placed Daniel Sturridge could not believe Ramires had nipped in ahead of him as the goal gaped.
That was the trouble though. Chelsea needed Torres to convert those chances, not create them. He eventually did. And then contributed to one of those bloopers videos that will haunt him for the remainder of his career.
As Chelsea pressed, United created nothing. Their opener already converted after slack marking that angered John Terry and must have alarmed Villas-Boas.
There was nothing special about Ashley Young's eighth minute free-kick, which was floated to the far post.
But Terry found himself the only one defending as United shirts piled in, Smalling the man to make a connection to turn home his first league goal.
Having escaped unscathed from Chelsea's pummelling, United went to the other end and doubled their lead thanks to a piece of brilliance from Nani.
Questions should be asked about the ease with which Juan Mata was brushed aside but once the midfielder was out of the way, Nani advanced with confidence and drove a 20-yard effort into the top corner.
By half-time, United had a third as Terry's attempted clearance bounced off Nani and into the path of Rooney, who tapped home his ninth of the season.
The credit went to Phil Jones, although the aura surrounding the summer arrival from Blackburn was punctured by the ease with which Torres got behind him to slot home Nicolas Anelka's through ball 30 seconds after the re-start.
It was only Torres' second goal since arriving from Liverpool and justified Villas-Boas' decision to introduce Anelka for Lampard at half-time.
Having already threatened on numerous occasions, Chelsea's confidence grew immediately.
United nerves would have been eased had they converted the penalty Jose Bosingwa gifted them when he tripped Nani after initially remaining static to allow the Portugal winger to seize on the loose ball after his own deflected shot had crashed against the bar.
Neither side will forget how Terry slipped as he went to slot home what would have been the decisive spot-kick in the shoot-out to decide the 2008 Champions League final.
Rooney emulated him, his standing foot giving way, the ball bouncing harmlessly wide after the striker had fired it into his own body.
United might easily have had another spot-kick when Cole flew into Hernandez after Rooney had pushed a glorious chance against the post.
The tackle was not great and resulted in Hernandez hobbling down the tunnel in obvious pain as he was replaced by Berbatov but, having fired into the side netting, Dowd felt the incident was worthy of a yellow card and no more.
Having scored once in front of the Stretford End, Torres suffered utter humiliation seven minutes from time as he raced on to Ramires' through ball, rounded De Gea and then somehow fired wide of a completely empty net.
Berbatov missed a golden opportunity himself in stoppage time, as Cole cleared off the line after Rooney had set the Bulgarian up with an admittedly misdirected pass.
Man Utd 3-1 Chelsea: Match Report - view commentary, squad, and statictics of the game as it happened.