The Red Devils made the trip to north London looking to end Arsenal’s impressive 13-game winning run at the Emirates Stadium in the Premier League.
Manchester United made the breakthrough in the fourth minute when Antonio Valencia beat Arsenal goalkeeper Petr Cech before Jesse Lingard doubled the away side’s lead.
The 20-time English champions came under pressure from Arsenal’s talented attack but Alexandre Lacazette, Mesut Ozil, Aaron Ramsey and Alexis Sanchez at The Emirates.
De Gea produced a staggering 14 saves to equal a Premier League record before Lacazette temporarily halved the deficit before Lingard’s third goal in the English capital.
The Manchester United goalkeeper was linked with a move to Real Madrid in the summer but the Spain number one opted to remain at Old Trafford beyond the summer transfer window.
And Mourinho lifted the lid on his post-match conversation with the Manchester United shot stopper following their impressive 3-1 win.
“I told him after the match, what I saw today was the best from a goalkeeper in the world,” Mourinho told BT Sport.
“You need the keeper to be there for you when the team needs. All the effort from the players was magnificent.
“The game, we started in one way and they started in another, then we changed and went down to 10 men and changed again.”
Manchester United are in second place in the Premier League table and five points behind current leaders Manchester City.
The Red Devils have only lost to Huddersfield Town and Chelsea in the Premier League this season.
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