Substitutes Marcus Rashford and Marouane Fellaini both scored as Manchester United overcame a resolute Leicester to strengthen their position at the top of the Premier League.
Jose Mourinho's side had applied incessant pressure on the Foxes from kick-off, and Romelu Lukaku missed a second-half penalty prior to the goals, as they found it difficult to break the steadfast backline.
They finally breached the last line of defence when Rashford converted Henrikh Mkhitaryan's corner three minutes after coming on.
And then midfielder Fellaini stuck out his knee to divert fellow substitute Jesse Lingard's drive past Kasper Schmeichel.
United are the only side to have won all three of their opening league games this season and have yet to concede a goal.