The Blues have struggled for consistency in the defence of their title this season and have slipped to shock defeats against Burnley and Crystal Palace.
But they were rewarded for their pressing style on Sunday afternoon when Alvaro Morata ghosted into the area and headed home from Cesar Azpilicueta's cross in the 55th minute.
Chelsea vs Manchester United: Player ratings
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"This is a team full of fantastic players and we need to take advantage of that and I think we struggled lately a little bit to defend a little bit too much and not have the ball enough," he told Sky Sports. "Today we had a lot of the ball, we created chances, we played like a big team, we defended like a big team and we have to be proud today.
"In my opinion if you play for Chelsea Football Club you need to win every single game. Chelsea-Man United is always a big game but you go to any stadium in the Premier League nowadays, it's difficult, we experienced it at Crystal Palace for example."
In a surprisingly open affair, United had opportunities to level late on, with substitute Marouane Fellaini, on his return from injury, taking a high ball down and drawing a fine low save from Chelsea goalkeeper Thibaut Courtois.
Jose Mourinho said: "I think they scored the goal in the only period where they were on top of the game."
Mourinho was once again left to lament the absence of several players for United's recent run of fixtures after his second-placed side slipped eight points behind runaway league leaders Manchester City.
"We are second, we are not fifth or sixth or seventh or eighth, so we have 18 teams in a more difficult position than we have. Eight points is eight points. We went through a very difficult phase with probably the most important matches - Tottenahm, Liverpool, Chelsea - without important players. I don't like to speak and it's not after a defeat that I'm going to speak but it is obvious through a difficult period with limitations."
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