Iheanacho was introduced for Jamie Vardy with 10 minutes remaining in the game.
Wilfred Ndidi was not included in the squad after he was replaced by Hamza Choudhury moments before the line-up was announced due to a sore knee.
The game was Iheanacho’s ninth in the league with three goals.
Harvey Barnes and Ben Chilwell were on target for Leicester while Antonio Rudiger bagged a brace for Chelsea.
Rudiger opened scoring for Chelsea on 46 minutes before Barnes equalised for Leicester on 54 minutes.
Chilwell put Leicester 2-1 ahead but Rudiger grabbed his second goal on 71 minutes, to rescue a point for Chelsea.
Leicester remain third on 49 points while Chelsea are fourth on 41, in the league table.