Bernardo Silva scored the only goal of the match 35 seconds into the second half at the Etihad Stadium when he prodded home at the back post from David Silva's low cross.
Chelsea's fourth defeat in five league games left Antonio Conte's reigning English title-holders five points adrift of the top four.
And the Italian's negative approach came under scrutiny after the visitors failed to register a shot on target after he again opted to start without a recognised centre-forward by leaving Alvaro Morata and Olivier Giroud on the bench.
"Today they showed the difference between them and us in this moment," said Conte.
"Twenty-five points is a big gap and I think that we can have a regret for the other games but not for this one.
"The effort of the players was an important effort. When you play against Manchester City, this type of team, they are showing fantastic quality but also fantastic mentality.
"When you match quality with mentality, you become unstoppable."
City now need a maximum of four wins from their last nine league games to seal the title and even manager Pep Guardiola admitted he is surprised by the extent of City's dominance.
"No way. Who could believe it?" Guardiola said of his side amassing 78 points from 29 games. "I think if you ask the players, the players neither."
Guardiola celebrated wildly at the full-time whistle as he senses his first Premier League title is now a matter of weeks away.
And he hailed his players' relentlessness not to let up despite their mammoth lead.
"I think we made an amazing performance because (it) is against Chelsea, the last champion.
"We were aggressive, we had desire, we had commitment to show we want to do it again and again, and that's why we won."
- Sane stands out -
Just as in a 3-0 win at Arsenal on Thursday, Leroy Sane was the inspiration for much of City's best attacking play.
Sane created the hosts' first big chance 21 minutes in when he slalomed past three Chelsea defenders before feeding Bernardo Silva, whose shot dipped just too late and dropped onto the roof of the net.
The German thought he had opened the scoring just before the half-hour mark when he caught Kevin De Bruyne's cross flush, but Chelsea captain Cesar Azpilicueta bailed out his side with an excellent goal-line clearance.
So anonymous were Chelsea as an attacking threat that their own fans sarcastically cheered when a rare foray forward earned a corner just before the break.
However, Conte's contain and counter-attack game plan was undone within a minute of the second period when Sergio Aguero's reverse pass picked out David Silva and his namesake Bernardo knocked the ball into the ground and over the helpless Thibaut Courtois for his seventh goal of the season.
Thereafter, City were quite content to keep possession as Chelsea still refused to abandon their cautious approach.
Conte eventually introduced Giroud with 12 minutes remaining, whilst Chelsea's club-record signing Morata had to wait until the final minute to get on.
But even then it was top scorer Eden Hazard who was sacrificed and the Belgian cut a frustrated figure as he trudged off in the pouring rain.
The visitors could, though, have snatched an unlikely point in stoppage time only for Marcos Alonso's mishit strike from the edge of the box to dribble wide.