Jamie Vardy was on target from the penalty spot as Leicester moved up to second in the Premier League following a 2-0 victory at hapless Tottenham.
Jose Mourinho's men were seen as the main challengers to defending champions Liverpool after a promising start to the season but they were second best in a limp display in north London.
Vardy's spot-kick on the stroke of half-time and a Toby Alderweireld own goal just before the hour saw Brendan Rodgers get one over his former mentor and saw his side move four points off the lead.
Although Spurs made it much easier for them than it should be, the victory at a team around them in the table sends a strong message.
For Tottenham, this defeat follows on from the one at Anfield in midweek and the manner of it validates Mourinho's opinion that they were never title contenders.
In Sunday's early kick-off, rock-bottom Sheffield United were cruelly denied a first league win of the season after substitute Danny Welbeck salvaged a 1-1 draw for fellow strugglers Brighton.
Albion forward Welbeck volleyed home three minutes from time as the beleaguered Blades had to settle for only a second point of a miserable campaign at the end of their 14th fixture.
Jayden Bogle's deflected second-half strike on his top-flight debut had put the visitors on course for an unlikely victory after John Lundstram's dismissal left them with 10 men for 50 minutes.
Chris Wilder's battling side could even have ended a tense contest empty handed as Alireza Jahanbakhsh headed against the crossbar deep into added time.
United sit eight points from safety after ending an eight-game losing streak, while Brighton move two points above the relegation zone as their alarming home form continued.