“Let Diego Costa play his football,” José Mourinho said in the heated aftermath of the narrow Capital One Cup victory over Liverpool, thereby surrendering the moral high ground and as good as admitting that the alleged refereeing and media campaign against Chelsea is in fact more of a Chelsea campaign against referees and the media.

Mourinho certainly had grounds for complaint in the second leg against Liverpool with Lucas Leiva and Jordan Henderson lucky to stay on the pitch after miraculously escaping second bookings and Costa clearly denied a penalty in the first half, but if the manager is not prepared to look at the other side of the coin – to consider that Costa was fortunate still to be on the pitch after his stamp on Emre Can – he has no real interest in fair play and talk of referees ganging up on Chelsea is just so much diversionary waffle.

One imagines the Football Association will be stirred into action over Costa, because while one stamp on an unprotected ankle may be considered accidental, or at least not proved to be deliberate, a second similar offence (on Martin Skrtel) removes the benefit of the doubt. Mourinho could lose a key player for the important game against Manchester City on Saturday, and try as he might, and probably will, he cannot pin the blame for that on referees. Or on the TV pundit Jamie Redknapp.

Costa is a tremendous asset to a forward line but he plays on the edge. He winds up opponents in a manner reminiscent of Luis Suárez, because the added bit of adrenaline that comes from being ultra-competitive for the whole 90 minutes brings out the best in himself. Presumably Mourinho knew that when he bought him, having had more opportunity to see him in action than Liverpool had when they bought Suárez. So either the Chelsea manager wants him to tone down his game or he is happy to see him continue being Mr Sneaky and running the risk of dismissals and bans. If it is the first, it is not working. If it is the second, Mourinho can hardly expect his side to be popular with referees, pundits and the media in general.

Most people like Costa, despite his imperfections, because an aggressive competitor will always be well received in this country. While clearly no saint, the Brazilian is pretty good at what he does, and much the same can be said of Mourinho. The manager is quite right to point out that his side have been on the end of some shocking decisions this season, and he is well within his rights to grumble about the standard of English refereeing, but the store of goodwill and admiration quickly runs out when he starts talking twaddle.

“I don’t know what you understand by a stamp,” he said of the Costa incidents, immediately insulting the intelligence of anyone who had seen the footage. “They [Sky] must be nuts [for referring to Costa’s crimes]. The opponent goes to the floor and he [Costa] puts his foot there, when he is looking at the ball.”

The fact that Costa committed the same offence twice, on different opponents, in different parts of the pitch, should give a broad clue as to who is being nuts there. Nor do the pictures, even the still ones, support the idea that Costa was looking at the ball. Sky’s studio pundits called the events as they saw them; even Mourinho accepted that their task is to be fair and honest. He just does not seem to like it when the fair and honest opinion is that some of Costa’s actions were criminal. In the context of a football game, that is.

There are millions of worse things that go on in the big world outside, but on a football pitch, when two of the best teams in the country are facing each other, it is quite hard to mount a defence of a player who appears to go around jumping on opponents’ ankles. As Redknapp said, Costa was “bang out of order”. Redknapp is not normally associated with trenchant views or acerbic criticism, but why on earth should he be evasive or noncommittal to protect Chelsea? The problem is wholly with Mourinho and his player.

Looking ahead to the weekend, the big question is whether Manchester City can mount as convincing a challenge as Liverpool at Stamford Bridge. On the basis of their last three games – one point that should have been more at Everton, no wins and no goals in subsequent home matches against Arsenal and Middlesbrough – the answer may well be no.

Chelsea appear to be struggling for their best form, especially in front of goal where Eden Hazard seems to have temporarily mislaid the capacity to be decisive despite a wealth of possession, but the same applies too to David Silva for City, and there are question marks over whether Sergio Agüero is back to his most effective best after injury.

City need a really big performance – a draw would not be the end of the world for Chelsea – and to do that they need all their big players to weigh in with telling contributions. Against Middlesbrough in the Cup last week, Silva, Agüero and Vincent Kompany were some way below the required level. In fact the latter was so unsteady in defence Manuel Pellegrini may feel he is not yet fully recovered.

The game could be close, though in all probability not as close as Chelsea v Liverpool. Fixtures between those two clubs in the last decade or so have taken on a life of their own. The rivalry has become one of the most absorbing in English football in spite of changing managers and an ever-widening circle of imported players. Consider this for instance: there were no few than seven Brazilians on the Stamford Bridge pitch in normal time, not to mention three Belgians, three Spaniards and just four English players, yet the game was the epitome of the end to end, all or nothing, winner takes all English cup tie. As a preparation for one of the most important league games of the season this Saturday it was absurd, and that may be one of the reasons for Mourinho’s evident frustration, though he has worked in the country long enough to know the score.

City must hope that even by Saturday a two-hour struggle will have taken something out of Chelsea, though Mourinho’s side have less reason to be gung-ho about the league match and the pace on Saturday may be a lot more sedate. An anticlimax possibly awaits. It is not that the Capital One Cup is bigger than the Premier League, just that Chelsea’s history with Manchester City is not yet as complex and storied as their dealings with Liverpool. There was no story in the league last season, Chelsea won both games. It is now up to City to alter the script.