Both Ndidi and Iheanacho, fresh from representing Nigeria on international duty, were thrust into the heart of the action.
Ndidi started and played the full 90 minutes, while Iheanacho entered the fray in the 74th minute, replacing Jamie Vardy with Leicester already trailing.
In a moment of brilliance, Iheanacho appeared to have equalized the game with a sublime chip over the Bristol goalkeeper, only for the assistant referee to flag for offside.
The defeat sees Leicester City slipping to third place in the league standings, having now suffered four losses in their last six league matches.
