Goals from N’golo Kante and David Luiz ensured that Chelsea gained all three points against the Champions in the Premier League.
Kante struck in first half stoppage time before Luiz sealed the points deep into the second half.
The win means they jump back into third while City have relinquished top spot to Liverpool after their 4-0 thrashing of Bournemouth.
After results earlier on Saturday sent Chelsea down to fifth, the Blues climbed back up to third and moved within eight points of Liverpool in top spot.
Sarri’s men showed steel and resilience to keep City at bay during the opening period, and their increased confidence steeled them to hold onto the display with a well-organised closing 45 minutes.
Their fellow title hopefuls will no doubt take notice.
We’re all feeling like @nglkante here! 😃
— Chelsea FC (@ChelseaFC) December 8, 2018
City’s early pressure looked certain to culminate in a goal, but a brilliant tackle from David Luiz denied Sane a great opportunity to open the scoring in the 15th minute.
The Brazilian has been inconsistent this season, but he remained solid in the second period and nodded home late on to seal what had initially appeared an unlikely victory.
With Aguero still sidelined due to a muscle injury and Jesus out of form, Guardiola decided to play Sterling through the middle.
However, the England international still spent most of his time playing from the right as City’s attack lacked cohesion despite them being on top for prolonged periods.
Guardiola changed things in 53rd minute and Sane can consider himself unfortunate he was the one hooked, while Jesus did not test Kepa until second-half stoppage time.
City will be out to wrap up top spot in Champions League Group F when they host Hoffenheim on Wednesday, while Chelsea will take on Vidi in the Europa League 24 hours later.