If Manchester City do win the championship in May, this is what it will look like; beach balls tossed around, the constant chants for Roberto Mancini and skies the colour of the shirt Carlos Tevez will never wear again.

The whole Tevez affair concealed the fact that Manchester City's introduction to the Champions League, which is what the Abu Dhabi oil money was for, is threatening to turn into a very brief encounter. Mancini stressed from the outset that they must avoid Tottenham Hotspur's pitfalls that saw them briefly light up Europe but slip badly in the games that followed. City, who have been drawn away after every one of their European fixtures, seem to be coping pretty well domestically.

It is just the Champions League they have problems with, which is in itself a strange echo of Mancini's time at the helm of Internazionale. At the end of the match here the Manchester City manager walked on to the pitch, applause to his right, a demonstration demanding Steve Kean's sacking to his left, bound for a flight back to Italy. With him was Mario Balotelli.

Now that Tevez has been denounced by Graeme Souness as "the epitome of everything the man in the street thinks is wrong with modern football", the young, mercurial Italian seems a picture of reasonableness. He was their most likely route to goal in a first half, when Manchester City seemed unable to wash away the taste of their defeat in Munich. After the interval he sent one shot curling on to the frame of Paul Robinson's goal and then finished off Blackburn and Samir Nasri's cross with brutal elegance.

He emphasised the depth of Mancini's resources. Tevez was finished, Edin Dzeko banished to the bench after his insipid display against Bayern Munich and midway through the first half Sergio Agüero pulled up with a groin injury that will keep him out for around three weeks. It is hard to think of any club that could cope without £90m worth of striking talent but Mancini did so by bringing on Nasri and moving Balotelli to a more central position.

"He is a man who can get 20 goals a season if he plays as a central striker," said Adam Johnson, whose goal had begun the rout on a day when the press office again banned questions about Tevez. "He's got all the attributes. It's just a case of putting it together week in and week out. His was a classic striker's goal and you don't really associate him with that. Some people think he is a bit fancy who scores great goals now and again but he is more than that.

"We showed some resilience. After everything that's happened [in Munich] a few heads could have gone down. We could have crumbled but this shows the strength of the squad we have here. After the restart we totally dominated."

Blackburn's good fortune lasted until the moment when Johnson trapped the ball with his lime-green boots, took one touch, heard Nasri shout: "Shoot!" and curled the ball into the top corner. It was very similar to the wonderful shot that had salvaged a point at Sunderland in March last year. "You could say it's a bit of a signature goal, a bit of a trademark," he said.

It triggered a damburst of resentment all over Ewood Park, where shouts for the dismissal of their manager became a crescendo. When the City supporters in the Darwen End began serenading Kean with a chorus of "You'll be sacked in the morning", it was met with applause from the remaining three-quarters of the ground. Kean is David Brent as a football manager. He cannot pass by a positive without accentuating it and wanted to emphasise the first 55 minutes rather than the abject final 35. Had he been captaining the Titanic, Kean would have announced to the passengers that he had taken a delivery of fresh ice for their gin and tonics and that they should concentrate on the first half of the voyage. He said the players were upset and angry at the abuse he had received from the crowd and had to be reminded that his players might be upset and angry at their own performances.