Alvaro Morata gave Manchester United a taste of what could have been by heading Antonio Conte's Chelsea to a much-needed victory as Jose Mourinho endured another frustrating Stamford Bridge return.
All eyes were on the touchline as the combustible managers faced off, with Manchester City's latest win leaving United eight points off the Premier League summit as pressure mounted on Conte just months after leading the Blues to the title.
Sky Bet have pushed United out from 9/1 to 14/1 to win the title and Chelsea have shortened from 28/1 to 20/1 to retain the trophy.
The Italian twice got the better of Mourinho at Stamford Bridge last season and made it a hat-trick in a tense encounter on Sunday, with Morata's fine header giving Chelsea a deserved 1-0 win against second-placed United.
It looked like the Spain international would instead be wearing red until Mourinho completed a summer move for Romelu Lukaku, whose goalless streak stretched to a seventh match as the Chelsea striker brought his scoreless run to a timely halt.
Having seen an early Phil Jones own goal ruled out because of his foul, Morata capitalised on lacklustre United defending to superbly head home Cesar Azpilicueta's cross in the 55th minute.
It was no less than Chelsea deserved as they pressed the issue against an increasingly ramshackle United, although Marcus Rashford and Marouane Fellaini went close to snatching a fortuitous point as the clock wound down.
Post-match reaction
Manchester United boss 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.
He said: "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 - Tottenham, 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."
The Portuguese confirmed he did not shake hands with opposite number Antonio Conte at the final whistle, adding: "He disappeared so I shook to his assistants."
On the handshake, Conte said: "It's not important. It's important to win the game. You have to have the respect on the pitch not outside the pitch.
"It's an important victory. When you play against Manchester United it's always a massive game. We know very well this team is very strong. This type of win is important for our confidence. We showed great desire and passion to win this kind of game."
The Italian has cast some doubt on David Luiz's future in west London after omitting the Brazilian from his matchday squad.
Luiz had been a regular in Conte's line-ups this season but 21-year-old Danish defender Andreas Christensen was preferred.
Conte said: "Christensen is the present and the future for Chelsea."
When asked whether Luiz has a future at Chelsea, Conte replied on Sky Sports: "I don't know. He has to work really hard otherwise they are on the bench or in the stand."
He failed to clarify his position at the post-match press conference, deflecting questions about Luiz by saying: "Are you talking about the future? But every day you put my future (in doubt)."
Conte insisted Luiz's omission was "only a tactical decision", the best for the team and praised Christensen.
"It's normal," Conte added.
"This can happen to every one of my players, if I see that they are not in good form."
Cesc Fabregas believes Chelsea played to the level he expects as the defending Premier League champions.
Fabregas told Sky Sports: "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.
"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."
