There was much debate before this showpiece fixture about the qualities of Diego Costa and Sergio Ageuro, and which striker one would choose if pushed to make a selection between the two.

It is a thought provoking if futile discussion about two world class forwards but some observers may be swayed after this compelling game, the most significant of the Premier League season so far and one that ended in utter pandemonium.

Costa walked off having turned the match around for Chelsea, while it was a rare afternoon when Manchester City trudged off ruing the profligacy of Aguero, sent off in injury time for a horrendous challenge on David Luiz.

Remarkably, Costa was even playing the peacemaker in the closing stages, when a mass brawl ensued on the touchline and Fernandinho followed Aguero in seeing red. A three-match suspension will surely follow for the Argentinian.

Neither side’s defences emerged smelling of roses. Both played a back three with varying degrees of success and with attacking opportunities plentiful. Space was found freely and chances came regularly.

For Chelsea, so solid at the back since their 3-0 defeat at Arsenal in September – when Conte reacted to that capitulation by switching formation to 3-5-2 – this was anathema. Nemanja Matic’s enforced absence and Cesc Fabregas’ starting berth may have explained something, but this was Chelsea’s most severe test yet in their new-look formation and they did not perform with anywhere near the same level of calmness in defence seen in their previous seven successive wins.

Equally, City were shaky and although Guardiola has utilised a three-man defence on more than one occasion this season, some of City’s strongest displays this season have come when playing the more familiar four at the back.

Sergio Aguero tussles for the ball with Victor Moses (Getty)

It was an unusual off-day for Aguero and a frustrating one in terms of some refereeing decisions. Luiz could have easily walked for his check on Aguero in the first half and there were penalty appeals when Ilkay Gundogan tumbled to the turf under the challenge of N’Golo Kante.

Aguero certainly had plenty of chances, but his usual clinical touch evaded him. By the time Costa had scored, created one and watched on from the bench as Eden Hazard made the points assured, the Argentinian had seen numerous opportunities come and go.

The predatory instincts demonstrated at Burnley last weekend, and indeed throughout the league campaign where he has scored 10 times so far, were absent. Aguero nodded Kevin De Bruyne’s precise cross narrowly wide of Thibaut Courtois' goal in the 43rd minute before coming closer at the start of the second half. At one stage he rounded Courtois only to be denied by the scrambling Gary Cahill – making amends for his earlier own goal – before the goalkeeper denied him with a smart save in the 62nd minute.

Loading....

For Costa, though, his rebirth continues apace. He is truly a transformed player in comparison to last season, now able to combine his ferocious physical intensity with a clinical touch and eye for a team-mate.

Chelsea were down and out, being outplayed before Costa brought them back into the game with a brilliant finish. He chested down Fabregas’ ball expertly, outmuscled Nicolas Otamendi before firing past Bravo.

He then had a key role in their second. City had been pressing themselves before a swift Chelsea break where Costa accelerated through midfield and laid a precise ball through to Willian who finished coolly.

Aguero is shown his marching orders (Getty)

Tottenham challenged Chelsea last week, but for Conte’s side this was an even more impressive performance. City provided a more stern examination and Chelsea dug deep to finish strongly after struggling for large parts of the game.