Ander Herrera scored one goal, set up another and executed the ideal man-marking job on Eden Hazard to set up Manchester United's 2-0 win over Chelsea that opened up the Premier League title race on Sunday.
Mourinho's Manchester United side stunned the league leaders with a 2-0 victory at the weekend, which helped the Red Devils exact revenge for the two previous wins Chelsea managed to secure over the club this season.
This time he was United's match-winner, setting up Marcus Rashford's seventh-minute opener and netting with a deflected shot early in the second half.
The performance also bodes well for the remainder of the season, with fifth-placed United four points behind their nearest rivals but boasting at least a game in hand on all of them.
Mourinho contended United had played better in a 1-1 home draw with Arsenal and 1-0 win over Tottenham.
United "showed more desire, more ambition, more motivation", said the Italian.
Mourinho's decision to man-mark Eden Hazard and Pedro effectively muzzled Chelsea, who failed to register a shot on target in a league game for the first time since 2007. But it is a great feeling to know it is hard for us to lose a match.
Chelsea looked to be strolling to the title just a few weeks ago - but a sudden stumble, including the home defeat by struggling Crystal Palace, and an irresistible surge from Spurs have brought renewed edge to the run-in.
They remain in the driving seat and will face only one top-seven side - Everton - in their last six games, but Conte suggested his team can no longer be considered outright favourites. "I don't think a lot of people expected it but we did".
Chelsea captain Gary Cahill joined Costa in the book in the opening moments of the second half for a challenge on Maurouane Fellaini - and soon afterwards United doubled their lead.
"Firstly, with the Liverpool and Manchester City victories, if we didn't win it's goodbye to the Premier League [finishing in the top four]".
"This kind of game gives us confidence". 'He is still very, very young and I think he is very important for us.
"When he does things quick I don't think there are many defenders who can live with him".
There hasn't been a player this exciting at Manchester United since an 18-year-old Cristiano Ronaldo signed for the club from Sporting back in 2003. "It is better to be in Chelsea's position than Tottenham position, that is for sure".