This season's Manchester City are maturing into a vintage to savour with every outing. The only side still in with a shout of an unprecedented quadruple, Manuel Pellegrini's team are a slickly smooth threshing machine that eases through the gears at will while piling up the goals for a tally that now stands at a breathtaking 99 in all competitions.

Having pushed Blackburn Rovers aside with ease, City meet Watford in the next round of the FA Cup on 25 January as Cardiff City, Saturday's visitors to the Etihad Stadium, already start to contemplate damage limitation.

Satisfaction was sealed here when Sergio Agüero ended a nine-game absence with a calf problem by coming off the bench after 72 minutes and promptly registering the fourth goal in this easy win.

Pellegrini was magnanimous when assessing the result. "We are really very happy but I think the difference between the two teams was not five goals today," he said. "We played with a very strong team. Blackburn played well in the first half, we didn't find space. It was important for us to score a goal at the last of the 45 minutes and in the second half we had space and opportunities to score but I repeat, congratulations to Blackburn because they were a very difficult team."

While it was Álvaro Negredo, the scorer of two along with Edin Dzeko, who registered that strike on the stroke of half-time, when City strode out for the second period they were merciless.

Of this Pellegrini said: "We continue playing a style of football that for us is very important to continue – not to score one goal and try to keep the ball. It is more easy to go back with 10 players and try to counterattack but it is not my philosophy, it is not the philosophy this club wants to play. We continue trying during 90-95 minutes every game to score, to be a very balanced team, an attractive team and not a destructive team. That is very important for me."

This was the problem facing Gary Bowyer's Blackburn side: City's relentless urge to keep on coming at sides, particularly in front of their own supporters, where they have been on a season-long goal rush terrorising just about all opponents, with the hammerings of Arsenal, 6-3, Tottenham Hotspur, 6-0, and Newcastle, 4-0, among their prize scalps.

If Bowyer secretly hoped to escape the Etihad without his side suffering severe damage he could hardly be blamed. Yet he could send out Blackburn having told them that they were the one team to have stalled the City juggernaut in their past 10 games – the 1-1 draw they managed at Ewood Park in the initial tie the only time Pellegrini's side had not won in this period.

Before the opener Rovers threatened on one or two occasions. Tom Cairney raced at Matija Nastasic and after being slipped past the defender conceded a foul near the D of City's area. Ben Marshall stepped up but placed the dead ball straight into Costel Pantilimon's hands, much to Bowyer's annoyance, the manager smacking his hands in frustration in the technical area.

Perhaps the visiting manager had identified the Romanian as a weak link as there had been an earlier moment when DJ Campbell put the goalkeeper under pressure by charging down a back-pass that Pantilimon only just managed to clear.

Negredo collected his 20th goal of the campaign when Fernandinho looped over a ball from the right and the Spaniard headed home to bring the familiar cries of "Beast" from the home crowd as the sides walked off for the interval.

The XI Pellegrini had sent out was missing Yaya Touré and David Silva, who have minor injuries, as well as Agüero and Samir Nasri, in a side that showed eight changes from the one the manager fielded against Newcastle on Sunday. As the second half began the Argentinian was spied warming up on the touchline and as he was regaled by the adoring crowd with cries of "Sergio, Sergio", Negredo decided he would quite like to score again.

This time Aleksandar Kolarov, on for Fernandinho at the break, put the ball through and the City No9 calmly collected a 21st in 31 appearances of what is starting to look like the best debut season in recent memory. When these numbers are put alongside the 19 Agüero had struck in 20 games before his calf injury, a glaring clue is found as to why City had 94 goals coming into this match.

Dzeko, whose radar had been off, proved he too could be lethal by scoring twice before the end. The first came when Jesús Navas controlled possession, scampered to the dead-ball line and fed Dzeko, whose crashing shot was as emphatic as his final strike in the rout.

When Cardiff arrive at the weekend Pellegrini can choose his captain, Vincent Kompany, after resting him for this one, and hope that both Touré and Silva will be available. "Vincent Kompany doesn't have any problem, he is fit for Saturday, and I will see tomorrow to be 100% sure but I suppose Silva and Yaya both of them will be fit," said the manager.