It was looking like one of them days for United until super subs Marcus Rashford and Marouane Fellaini scored in the final 20 minutes of the game to seal the three points.
Romelu Lukaku also missed a penalty for José Mourinho's men but it didn't matter in the end as the Red Devils won for the third successive game, while the Foxes will be disappointed with their performance at Old Trafford.
Mourinho made one change while the Foxes remained unchanged
Mourinho made one change to his starting lineup for the game with Anthony Martial coming in to replace Rashford, while Craig Shakespeare named an unchanged lineup for the game after overseeing his side's win against Brighton & Hove Albion last weekend.
Brilliant saves from Schmeichel kept the Foxes in the game at half-time
In terms of the game itself, it took a while to get going until United started to control the game midway through the first half with Kasper Schmeichel proving to be a thorn in their side.
Lukaku was the first to be denied from the edge of the box and then a few minutes later after making the chance for himself, Juan Mata saw a brilliant curling shot brilliantly saved by the Danish keeper.
Paul Pogba also showed his confidence for United in front of goal as he has a number of long shots that just went wide of the goal with Schmeichel beaten on these occasions.
The Foxes, on the other hand, rarely threatened in the first half as they decided on their gameplan to sit deep and try and catch the home side on the break.
Therefore at half-time, the teams were deadlocked with both managers wanting more from their players in the second half in order to find the all important breakthrough in the game.
Lukaku's penalty miss added to United's frustration
The frustration continued for the home side at the start of the second half when Lukaku missed from the spot after referee Michael Oliver pointed to the spot when Danny Simpson handled Martial's cross.
Super subs Rashford and Fellaini scored late on to secure victory for United
Just as it looked like being one of them game's once again for United though, Rashford, who was only on the pitch for just over three minutes, volleyed home from a Henrikh Mkhitaryan corner to give United exactly what they deserved.
The whole stadium breathed a huge sigh of relief when United opened the scoring but they knew from the experiences of last season that the team needed a second goal in order to seal the win.
United did just that when Fellaini, who was only on the pitch for six minutes, diverted Jesse Lingard's cross into the back of the net to give United the breathing space that they needed in the game.
After the second goal, the hosts took their foot off the pedal for the first time in the game and that almost resulted in the Foxes getting one goal back in injury time when a cross from Demarai Gray was diverted torwards goal by Andy King but somehow David de Gea managed to save the ball with his feet to make sure of a third consecutive clean sheet this season.
That was the last attack of the game as the referee blew his whistle to bring an end to the game as United secured a third victory in a row just before the international break which was so important.