Manchester United's 100 per cent start to the season continued as the Red Devils claimed a 2-0 win over a stubborn Leicester City side.
The hosts dominate the first half, but had nothing to show for it, despite the best efforts of the busy Paul Pogba.
Mourinho's men thought theyhad a breakthrough shortly after the break when Danny Simpson handled inside the box, but Kasper Schmeichel was on hand to save Romelu Lukaku's spot kick.
The introduction of Marcus Rashford was what changed the game however, as the young striker netted three minutes after coming on to seal the points for the Red Devils.
Fellow substitute Marouane Fellaini sealed the deal when he tapped in a Jesse Lingard cross.
Here are five talking points from Old Trafford...
1. Rashford the difference maker
For all their dominance in the first two-thirds of this game, the Red Devils had to rely on Rashford to make the breakthrough.
The England striker immediately used his pace to trouble the Foxes defence after they had held firm in the face of increasing pressure.
Rashford's goal came after a dominant performance from United, which was a far cry from the languid performances seen at Old Trafford last season.
A big part of this is Paul Pogba's new role. He had six shots in a 16 minutes spell in the first half and on another day would have bagged at least a couple.
2. Maguire keeps Lukaku at bay
What better way to celebrate your first England call-up than by testing your chops against the likes of Romelu Lukaku and Paul Pogba?
That was the task facing Leicester defender Harry Maguire at Old Trafford this evening and the former Hull man showed why he has made his way into Gareth Southgate's plans.
Aside from a couple of shaky moments - a Mata nutmeg after 20 minutes and conceding a free-kick in a dangerous position after failing to cope with the physicality of Lukaku - he was a big part of the reason why Leicester kept United at bay.
3. Bailly the cornerstone of the United defence
While United dominate proceedings going forward, one of their best performers was at the back.
Eric Bailly snuffed out the threat of Jamie Vardy, easily matching the speed and strength of the England forward and was also a big part of why Riyad Mahrez was so ineffective for the visitors.
The Ivorian is settled in this side and he is now the rock on which Mourinho should build his defence.
4. Martial puts a shift in
Almost two years into his Manchester United career, Anthony Martial replaced Marcus Rashford in the starting XI, as Jose Mourinho made only one change from the side that saw off Swansea 4-0 last time out.
The Frenchman put in an industrious shift and his work rate was rewarded when he won the penalty which Lukaku would go on to miss.
He provided width for the Red Devils and put in the kind of shift that Jose Mourinho is a fan of.
5. Schmeichel makes himself at home
Kaspar Schmeichel playing at Old Trafford will always be an obvious subplot of any game and the son of Peter was given a warm reception by Jose Mourinho in the tunnel before kick-off.
The Foxes stopper was called into action early and often once the action got under way. His 20th minute save from Mata was superb and his excellent penalty save from Lukaku kept his side in it.
And that means he now has more penalty saves at Old Trafford than his old man - just the one, but facts are facts.
Next time those De Gea back to Madrid rumours pipe up again, the Dane will no doubt be linked with a move to his father's former side.