Chelsea endured a third successive goalless draw in an enthralling encounter against excellent 10-man Leicester.
Antonio Conte had been wary of the Foxes and his concern proved well founded as the movement and energy of Riyad Mahrez, Jamie Vardy and Shinji Okazaki troubled Chelsea.
Leicester were relentless, playing like champions, with the intensity of their pressing forcing mistakes.
Ben Chilwell was sent off for two bookable offences in quick succession, leaving the visitors down to 10 men with 22 minutes remaining.
Yet still Chelsea, who had won their previous seven Premier League home games since September's loss to Manchester City, could not break the Foxes down as the Blues followed stalemates with Norwich and Arsenal with a third in a week.
Conte tinkered with his defence for the visit of Chelsea's predecessors as champions.
David Luiz was Conte's first choice in the centre of his back three in last season's title-winning campaign.
Now the Brazilian is apparently not even second choice as Gary Cahill was deployed in the central role, with Andreas Christensen rested on the bench alongside Luiz.
Cahill lasted just 33 minutes before going off clutching his right hamstring.
He had been given a torrid time by Vardy, who showed no signs of the groin injury which deprived him of a return to his former club Fleetwood a week ago.
The Foxes cut through their hosts time and again, with left-back Chilwell creating chances for Okazaki and Vardy, who next dragged an effort wide across goal.
Wilfred Ndidi's free header was saved by Thibaut Courtois before Cesc Fabregas forced a save from Kasper Schmeichel at the other end.
Only a well-timed Cahill tackle stopped Mahrez from shooting following a mazy run and then Eden Hazard should have punished the Foxes at the other end, only to shoot tamely at Schmeichel.
A race with Vardy culminated in Cahill stretching for the ball before hobbling off. Christensen went on, with Luiz not even asked to warm up.
Mahrez then drilled the ball across goal, but there was no-one in a black and gold shirt to convert.
Vardy then robbed Antonio Rudiger inside his own box. The ball went to Okazaki, whose effort was blocked into the path of Marc Albrighton. He fired wide.
Schmeichel saved from Fabregas before the break and Leicester continued to pressurise their hosts on the resumption.
Vardy nicked the ball off Christensen and found Mahrez, who initiated contact by kicking the Denmark defender.
The Foxes forward went to ground, seeking a penalty, but referee Mike Jones was unmoved and not inclined to dole out a yellow card for diving.
Mahrez next blasted a shot into Christensen and it deflected wide.
Conte had seen enough and made his final two changes. Willian and Pedro were sent on for the ineffective Hazard and Fabregas.
Willian lured a foul from Chilwell, who was booked after 63 minutes.
The left-back then caught Victor Moses late and was sent off after 68 minutes.
Long-range shots from Kante and Tiemoue Bakayoko were symptomatic of Chelsea's struggles to break Leicester down.
And Schmeichel turned a Marcos Alonso free-kick behind for a corner in stoppage time as Chelsea missed their last chance.