ROVERS suffered a second-half collapse as they were knocked out of the FA Cup after becoming the latest side to suffer a heavy defeat to ruthless City.

The third-round replay at a rain-lashed Etihad Stadium remained level until added time at the end of an even first half when Alvaro Negredo struck to give Manuel Pellegrini’s quadruple-chasing team an undeserved lead going into the break.

But the floodgates opened after the restart as Negredo netted his second before Edin Dzeko bagged a brace of his own and Sergio Aguero marked his return from injury with a goal.

Dzeko's second goal was City’s 99th of an incredible season which has now seen them win 15 of the 16 home matches they have played.

Against such a free-scoring side who are averaging four goals a game in front of their own fans, the last thing Rovers, without skipper Scott Dann and top scorer Jordan Rhodes with minor injuries, needed to do was to concede early.

But that is exactly what would have happened had Dzeko been able to take advantage of two instances of slack marking in the opening 10 minutes.

On both occasions, however, Dzeko fluffed his lines, heading over a James Milner cross when unmarked in the box before firing over from 20 yards after a raking Fernandinho pass, which cut the new-look Rovers centre-back pairing in two, was touched into his path by Negredo.

But those lapses in concentration aside, the visitors, roared on by a magnificent 4,000-strong travelling support, would have been pleased by the start that they made.

It was not until the 26th minute that Paul Robinson was called into action as he palmed away a 25-yard Javi Garcia daisy-cutter which zipped off the greasy surface.

By that stage disciplined and determined Rovers had begun to make inroads into the City half and Ben Marshall will have been disappointed to send a free kick straight into the arms of Costel Pantilimon after a stirring, lung-busting run from Tom Cairney was abruptly ended by Matija Nastasic 20 yards from goal.

Although lone-striker DJ Campbell was yellow-carded – his first booking since his arrest and subsequent bail by police probing spot-fixing allegations – there was nothing desperate about Rovers’ defending and City’s frustration was evident when Dzeko hammered wildly over from 40 yards.

Yes they twice went close from teasing crosses from Jesus Navas and Milner, the latter which Dann’s replacement Matt Kilgallon left for Robinson who watched on in horror as the ball drifted agonisingly past his far post.

But it still came against the run of play when last season’s losing finalists went ahead on the stroke of half-time – just as they had done in the initial 1-1 draw between the teams.

And once again it was Negredo who did the damage, the Spanish forward thumping home a header from an inviting Fernandinho cross from the right to take his tally for his debut campaign in English football up to 20.

It was cruel on Rovers – and salt was rubbed into their wounds when goalkeeper Robinson had to come off injured at half-time, to be replaced by Simon Eastwood.

And Eastwood’s first act was to pick the ball out of the net as Aleksandar Kolarov played a wonderful pass behind the Rovers defence which stand-in skipper Grant Hanley missed, allowing the predatory Negredo to lift a nonchalant finish over the replacement goalkeeper.

Any hope Gary Bowyer’s boys had of bouncing back off the ropes, just like they did at Ewood Park, had seemingly evaporated.

But after weathering a storm they created three good chances midway through the second half.

The first two fell to Josh King, a 59th-minute replacement for Campbell.

The Norwegian flicked the first one over with his head after Marshall cut inside and whipped in a cross.

King should have done better, although he so nearly made amends when he raced on to a threaded Cairney pass and forced Pantilimon into a fine stop low to his left.

The impressive Cairney then set up Jason Lowe for a 20-yard effort which took a deflection before skimming the post.

It came as a sucker-punch, then, when City extended their advantage courtesy of the previously wasteful Dzeko, who collected a cutback from Jesus Navas and hammered an unstoppable shot in off the bar.

The hosts, who have now won their last 11 home games, were sensing blood and brought on the fit-again Aguero.

And, within 50 seconds of his arrival, the Argentinian hitman took a pass from Dzeko, spun in a crowded box before sending a low left-footed strike underneath Eastwood.

The Rovers goalkeeper was beaten again six minutes later as Dzeko delicately turned in his second from another Jesus Navas centre.

But the match, at least, finished on a high note for one Rovers player as 16-year-old Connor Mahoney, a recent arrival from Accrington Stanley, came off the bench to make his debut for the club he has supported all his life and he didn’t look out of place against established England international Joleon Lescott.