Leicester moved top of the Premier League by inflicting another damaging 2-0 defeat on Chelsea, to leave manager Frank Lampard fighting to remain in charge at Stamford Bridge.
The Blues have now won just two of their last eight league games to fall to eighth, nine points behind the leaders.
Chelsea were expected to challenge for the title after a £220 million ($298 million) spending spree in the transfer market.
But it is Leicester who are threatening to recreate their heroics of the 2015/16 season when they shocked the world to win the Premier League.
A second title in five years would be less of a surprise, despite the financial gulf between the Foxes and the traditional top six in the English top-flight, as they have established themselves as a force to be reckoned with since Brendan Rodgers took charge nearly two years ago.
Lampard left two of his expensive summer arrivals in Timo Werner and Hakim Ziyech on the bench, but club-record signing Kai Havertz did return with former Leicester midfielder N’Golo Kante ruled out by injury.
Kante was one of the stars of Leicester’s title triumph, but Wilfried Ndidi has proved a worthy successor as a midfield enforcer and got the hosts off to a flying start with a rare goal.
