Ancelotti, back in the dugout after visiting his seriously ill father in Italy in midweek, watched his side produce a fabulous performance against ragged Rovers to go two points clear at the summit.
Chelsea destroyed Sam Allardyce's side with two goals from Frank Lampard, one apenalty, plus others from Didier Drogba, Michael Essien and an own goal from Gael Givet.
Dejection: Gael Givet reacts after his own goal
The game was so one-sided that had Chelsea taken all their first half chances, the scoreline could have been in double figures.
But four goals in a 15-minute second half spell handed Rovers theirbiggest defeat since Allardyce took charge at Ewood Park and keptAncelotti's 100 per cent home record intact.
Joe Cole, making his first start since January, should have openedthe scoring for Chelsea within the opening minute but he somehow headeda cross from Lampardwide of the target from six yards.
Lampard was inches away from giving Chelsea the lead in the 10th minute when his 20-yard shot just evaded the far post.
But Chelsea broke the deadlock in the 20th minute with a goal of classic simplicity.
A Blackburn attack broke down allowing Michael Ballack to collect the ball in midfield.
The Germany captain fed Nicolas Anelka on the left flank with asuperb low pass and when the France international crossed the ball intothe six-yard box, it was turned past his own goalkeeper by theunfortunate Givet.
Back in the goals: Frank Lampard celebrates scoring his first for Chelsea
Blackburn had to rely on counter-attacks and in the 25th minute theyalmost grabbed an equaliser but Morten Gamst Pedersen's 20-yard effortflashed wide of Petr Cech's right-hand post.
Chelsea's players were lining up to shoot and Essien tried his luckfrom 25 yards in the 29th minute but although the ball dipped violentlyin the air, it still went over the crossbar.
Lampard wasted another chance to increase Chelsea's lead momentslater when Ballack's cross found him unmarked on the edge of thesix-yard box. But the England midfielder put his header wide of thetarget.
In the 33rd minute, Rovers goalkeeper Paul Robinson came to their rescue when Lampard fed Anelka inside the penalty area.
A second goal seemed on the cards but Anelka's shot hit Robinson in the chest, much to the frustration of Ancelotti.
It was shooting practice for Chelsea and Robinson did well to punch away a 35-yard blockbuster from Drogba.
Five minutes before the break, Anelka turned and twisted before firing an 18-yard shot into the sidenetting.
Pure delight: Michael Essien celebrates with his team-mates after scoring Chelsea's third goal
Pedersen was the first player into the notebook on the stroke ofhalf-time for a foul on Branislav Ivanovic. Seconds later Robinsonpulled off a magnificent save to deny Lampard again.
Chelsea, somewhat predictably, went further in front in the 48th minute through Lampard.
The England midfielder scored his first goal in open play in the topflight since last April when he finished off a fine Chelsea move.
Essien sent Drogba racing into the penalty area and his cross wasonly half cleared by Lars Jacobsen, leaving Lampard to pick his spotfrom eight yards.
It was 3-0 in the 51st minute when Essien sent a 35-yard shot thundering beyond the despairing dive of Robinson.
Five star: Didier Drogba celebrates scoring Chelsea's fifth goal
Anelka then tried to repeat the feat in the 54th minute and his20-yard shot was so fierce that Robinson had to save at the secondattempt.
It got worse for Rovers in the 58th minute when Ryan Nelsen brought down Drogbainside the penalty area and Lampard converted the spot-kick for his second of the game.
Drogba underlined Chelsea's superiority in the 63rd minute when he rose highestto head home a corner by Lampard to make it 5-0. It was the Ivory Coastinternational's eighth goal of the season.
In the 67th minute Chelsea replaced defender Ricardo Carvalho with youngster Jeffrey Bruma for his Premier League debut.
Cole was then replaced by Daniel Sturridge, making his home leaguedebut, in the 76th minute. Cole received a standing ovation from thefans and a bear hug from Ancelotti.
The England midfielder had shown he was back to his best during an afternoon when Chelsea returned to top form.
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