Robbie Savage: How Mourinho's tactical triumph sank Man City
In his regular BBC Sport column, Robbie Savage looks at Chelsea's stunning victory over Manchester City.
I was at Etihad Stadium for BBC Radio 5 live on Monday night to see Chelsea manager Jose Mourinho get his tactics spot on, again.
I thought Mourinho would park the bus and concentrate on stifling City and killing the game but, from the start, his side showed plenty of attacking intent.
Chelsea completely controlled the game and carried out his plan to perfection. Man for man, in every department, they were absolutely brilliant.
No team has scored more than City at this stage of a Premier League season and they came into the game with a 100% winning record at home, but they did not look like they believed they could score a goal.
Mourinho completely out-thought City manager Manuel Pellegrini, and Chelsea completely outplayed City. They should have won by a bigger margin and we saw how much your formation and system matters, not just how good your players are.
Demichelis a disaster in defence and attack
From the start, Chelsea showed far more ambition than they had when they drew 0-0 with Manchester United and Arsenal at Old Trafford and Emirates Stadium earlier in the season. They got more men forward on Monday than they did in either of those games.
Mourinho's gameplan was to defend in numbers and then counter-attack with speed.
He set up in a 4-2-3-1 formation, with David Luiz and Nemanja Matic staying deep to protect his defence, and the four front players told to push forward and get a goal.
Eden Hazard usually started on the left and came inside, and Willian would also move into a more central area behind Samuel Eto'o when Ramires joined in.
With Fernandinho injured, Pellegrini put centre-back Martin Demichelis in central midfield and brought Matija Nastasic back into his defence.
Both were obvious weak links in the City side, but Demichelis was doubly disastrous because he affected his own team going forward as well as struggling to cope when Chelsea attacked.
Usually, when City go forward they do so at pace and move the ball about quickly, sometimes taking only one touch to lay it into the path of a team-mate and breaking into the box at devastating speed.
Previously, Demichelis has done all right when he has played in midfield for City but, against Chelsea, he was not in tune with their style of play. He took too many touches and slowed them down.
With Chelsea's forward players pressing high up the pitch, Demichelis also put his defence under pressure with some poor passing, and his lack of pace offered his back four little protection when Blues players ran at him.
He failed to get a tackle in on Hazard out on the left in the build-up to Chelsea's goal, and also failed to follow Hazard when he wandered across to the opposite flank just before Branislav Ivanovic scored.
Demichelis had a disastrous night, but were City's struggles in midfield all down to him? I am not so sure.
Matic and Luiz stop Man City in the middle
When I talk about tactics, sometimes people tell me that the game is not about formations, it is about the players.
But I think we saw at Etihad Stadium that systems do matter and, against the top teams and the really top managers in the really big games, a 4-4-2 formation is not the way forward.
I would not quite go so far as saying it is a tactic from the 19th Century but, at the Etihad on Monday, we saw City getting outnumbered in a key area of the pitch.
With Yaya Toure further up the pitch, Demichelis often had to deal with three fast Chelsea forwards running at him in the middle of the park and, even when they were not attacking on the break, the Blues' forwards found plenty of space outside the City box.
Compare that to the cover Chelsea gave their back four, with Matic and Luiz cutting off the supply line to their strikers, and Hazard, Willian and Ramires all tracking back to help their full-backs too.
Those three kept David Silva quiet, while Matic handled Toure superbly. Between them and John Terry and Gary Cahill in defence, they completely bossed the central area of the pitch.
Toure was playing further forward than Demichelis, but the reason he was so quiet was that Matic was so strong, working hard and taking up such good positions too.
It meant Edin Dzeko and Alvaro Negredo were not given any service and had no balls into the box to attack.
Hazard leads lethal Chelsea on the break
All of Chelsea's forward players were effective and all of them worked hard defensively too.
Hazard was given the most freedom to roam when they attacked but he fits perfectly into Mourinho's system as a player who is disciplined when it comes to closing down the opposition.
You have to earn your place in Mourinho's team with what you do with defence and attack and Hazard definitely does that. Nobody in the Chelsea side touched the ball more times than him on Monday.
We saw last year that he is an exciting attacking player but he is more consistent with his final ball now too. He tormented City's defenders and at times he was showboating too.
You can tell he is enjoying his football and enjoying the role he is being asked to do. He will have a big part to play in the title race.
As for City, well Pellegrini has played two different systems against Chelsea in the league, and has now been beaten twice.
He will have to try something different again when the Blues return to Etihad Stadium in the FA Cup on 15 February, and I cannot see him going with two up front against Mourinho again.