The irrepressible duo of Jamie Vardy and Riyad Mahrez again scored Leicester’s goals to send them two points clear at the summit and inflict a ninth league loss of the season on the champions, leaving Jose Mourinho’s men 20 points behind and only one point above the relegation zone.
The meeting was in stark contrast to the last clash between the sides at the King Power Stadium at the end of April when a 3-1 win put Mourinho’s side on the brink of the title and left the Foxes’ survival hopes in the balance.
As has been the case so far this season, Leicester looked inspired and Chelsea jaded and lacking imagination.
Mahrez got the home fans off their seats in the second minute with a mazy run in-field from the right before forcing Thibaut Courtois to get down to his left to smother his shot .
Wes Morgan’s sliding challenge to block a goal-bound effort from Eden Hazard was timely, but moments later Leicester were dealt a blow when Danny Drinkwater hobbled off holding his hamstring. He was replaced by former Chelsea schoolboy Andy King.
It was Chelsea’s turn to make an enforced change after half an hour when Hazard appeared to hurt his hip under a challenge from Vardy. Mourinho introduced Pedro.
Vardy’s next involvement hurt Chelsea further. Mahrez spotted the striker’s clever front-post run and found him with a lovely curling cross from the right which Vardy dispatched first time on the volley to give Claudio Ranieri’s side a 34th-minute lead.
Chelsea were almost level immediately as Nemanja Matic’s header from a corner clipped the top of the crossbar on the way over.
Marc Albrighton tested Courtois with a curling effort just before half-time and it was his superb deep cross from the left flank at the start of the second half that set up Mahrez for the second goal. The Algerian’s first touch to bring the ball under his spell was instant. He then turned Cesar Azpilicueta one way then the other until he had the yard of space he needed to bend the ball into the far corner of the net.
The King Power was rocking, but it was nearly silenced twice either side of the hour-mark when Pedro was crowded out in a goalmouth scramble before Kasper Schmeichel diverted Diego Costa’s shot over the bar when the Chelsea striker was through on goal.
Mourinho then brought on Cesc Fabregas and Loic Remy, with John Terry and Oscar making way, and two of his substitutes combined to get the visitors back in the game after 77 minutes as Remy headed home Pedro’s cross from close range.
Remy sent a shot wide from the edge of the area, but the champions could not force an equaliser despite some late pressure.
It was Chelsea’s first defeat to Leicester since February 2001. The man in charge of the London side that day? Current Leicester boss Ranieri.
Leicester City: Schmeichel, Simpson, Morgan, Huth, Fuchs, Mahrez (Inler 82), Drinkwater (King 17), Kante, Albrighton, Ulloa, Vardy (Okazaki 88). Subs not used: Dyer, Wasilewski, Benalouane, Schwarzer.
Chelsea: Courtois, Ivanovic, Zouma, Terry (Fabregas 53), Azpilicueta, Ramires, Matic, Willian, Oscar (Remy 65), Hazard (Pedro 31), Costa. Subs not used: Begovic, Mikel, Kenedy, Cahill.