Enzo Maresca’s side produced a devastating display of attacking football to move three points clear at the top of the table.
Knight opened the scoring with a deflected strike from distance which gave him his third goal in as many games, with Nmecha adding a second from the penalty spot after Danny Simpson fouled Sam Edozie.
Delap scored twice in 10 minutes to ensure City went in four goals to the good at half-time.
Played in by Edozie, he opened his account with a powerful drive across goal and then picked out the bottom corner with a precise finish inside a crowded penalty area for his second.
The striker then turned provider as Alex Robertson added a fifth before Nmecha scored the best goal of the game with a superb 20-yard half-volley that flew into the top corner.
Leicester grabbed a consolation in added time when Jacob Wakeling converted a penalty following Callum Doyle’s foul.
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