Chelsea extended their winning run in the Premiership to 10 matches after coming from behind against Sunderland, and despite Arjen Robben's red card.
Robben scored Chelsea's winner with a deflected shot but was immediately dismissed for celebrating with the fans and receiving a second caution.
Sunderland had taken the lead through Liam Lawrence's fizzing drive before Hernan Crespo levelled with a header.
Keeper Kelvin Davis performed heroics to deny Chelsea before Robben's strike.
It proved to be the Dutchman's last contribution as he was ordered off, seemingly for embracing some of the Chelsea crowd.
For a while it had seemed those fans would have little to celebrate as a stubborn Sunderland refused to roll over.
And the hosts even had the temerity to belie their bottom-club status and take the lead against the Premiership's runaway leaders.
Lawrence and Julio Arca were a real menace down the flanks and Chelsea's defending from crosses lacked its usual assurance.
And it was a punted ball into the centre from Arca which led to the opening goal on 12 minutes.
John Terry could only weakly head the ball out to Lawrence, who arrowed his shot past Cech.
It stunned the visitors - and possibly Sunderland, too - yet the expected Chelsea onslaught did not materialise.
Sitting deep and inviting Chelsea on, the Black Cats were content to watch their opponents play keep-ball.
Jose Mourinho's men did find a way through on 28 minutes, when Crespo reacted fastest to Cole's headed knock back across goal to nod the ball in.
But their oddly-subdued attack was easily smothered by Sunderland.
That is until the second half, when a different Chelsea emerged.
Davis put on a one-man resistance show as Chelsea pummelled their way past his defenders.
He made saves from Frank Lampard, Asier del Horno and Robben - and a tremendous reflex stop from a close-range header from Crespo.
How Sunderland must have rued Anthony Le Tallec's failure to score with a free header at the end of the first half.
But now it was only ever going to be Chelsea who would score again.
Yet it took a wicked deflection for them to do so, and beat the unfortunate Davis.
It was Dean Whitehead who tried to divert Robben's shot away from goal but succeeded only in glancing the ball out of Davis' reach.
Now a goal behind, but surprisingly with a one-man advantage, Sunderland attempted to claw their way back.
But Chelsea held firm to move a step closer to the title.
"We got just reward for a positive start. I know we were under pressure in the second half but you would expect that - they are better than us.
"It hurts to lose to a deflected goal but there is nothing you can do."
"In the second half before we scored the goal, we had a very strong 20-25 minutes and four or five big chances in a two or three-minute period.
"We played unbelievable football in that period and after we got 2-1 up, normally the game is over, but we went down to 10 men and we had to fight until the last moment."
Mourinho backs Robben red card
Sunderland: Davis, Hoyte, Breen, Caldwell, Danny Collins, Lawrence, Whitehead, Miller, Arca, Le Tallec (Gray 81), Stead (Murphy 81).
Subs Not Used: Nosworthy, Alnwick, Bassila.
Booked: Stead.
Goals: Lawrence 12.
Chelsea: Cech, Gallas, Ricardo Carvalho, Terry, Del Horno, Gudjohnsen (Huth 83), Makelele, Lampard, Joe Cole (Duff 63), Crespo (Carlton Cole 72), Robben.
Subs Not Used: Cudicini, Diarra.
Sent Off: Robben (70).
Booked: Robben, Carlton Cole.
Goals: Crespo 28, Robben 69.
Att: 32,420
Ref: C Foy (Merseyside).