Rovers' woes on the road show no sign of abating after losing 4-1 at Eastlands on Monday evening.
It was a game where they had only themselves to blame as each of City's four goals, including a Carlos Tevez hat-trick all came about from defensive errors.
City scored as early as the 7th minute when a Petrov corner was spilled by Paul Robinson and Tevez forced home from Benjani's knock back.
A second was added just before the break when Micah Richards raced from inside his own area to score after Benjani's effort had struck the post.
The second half started as badly as the first when a Benjani cross was allowed to travel a long distance to Tevez, and he swept the ball home with aplomb.
Rovers rallied to their credit, and for a while after Morten Gamst Pedersen had pulled a goal back there was a glimmer of hope they could get something out of the game.
But the final word was rightly with Tevez, when from a misplaced Rovers throw, the Argentine took full advantage with a tremendous finish.
Sam Allardyce welcomed back Brett Emerton, Lars Jacobsen, David Dunn and Franco Di Santo as he made four changes from the side that last started in the league at the close of 2009 against Sunderland.
The changes saw Pascal Chimbonda and Junior Hoilett drop to the bench, whilst a knee injury forced the absence of Jason Roberts and Benni McCarthy who sustained a back injury in the warm-up.
The injury to McCarthy was a blow pre-match and just seven minutes in it was City's Carlos Tevez who was delivering his own.
A poor back pass from Chris Samba couldn't be kept out by Paul Robinson, and from the resulting corner kick from Martin Petrov the Rovers goalkeeper flapped at the cross allowing Benjani to hook the ball back into the danger area for Tevez to lash home his eighth goal in eight games from close-range.
For a while City threatened to run riot as the Rovers back line struggled to cope with pace and energy of Petrov, Bellamy and Tevez, but to their credit they weathered the storm.
However they created little as an attacking force, Morten Gamst Pedersen and Gael Givet both volleying wide of goal in rare opportunities.
But just as it looked like Rovers would make their way in at the break just the single goal behind, more hesitancy saw them go further behind.
The goal came from the unlikely figure of City centre half Micah Richards, who ran unchallenged from inside his own half to feed Benjani on the edge of the Rovers box. The City striker saw his effort strike the inside of the post, but as the ball rolled invitingly across the area it was Richards saw his quick reactions rewarded as he forced the ball into the net.
Obviously unimpressed with his side's first half showing, Sam Allardyce made a double change at the break, with Junior Hoilett and Niko Kalinić thrown into the fray with Keith Andrews and Franco Di Santo making way.
But neither player had seen much of the ball before City were celebrating once more.
A ball down the right saw Benjani get the better of Gael Givet on the right, his centre should have been cut out long before the ball arrived at the feet of Carlos Tevez but there was no doubting the quality of the finish as the Argentine lashed a stupendous shot leaving Robinson with no chance.
The former United forward had a great chance to notch his hat-trick just before the hour mark, but he inexplicably headed wide Zabaleta's cross pinpoint cross.
A third change was made from Allardyce as Martin Olsson came on for David Dunn on 66 minutes and that prompted Rovers best spell of the game.
Two minutes later some impressive passing play saw Brett Emerton find Gael Givet, then Hoilett found Emerton in the area but Given made a smart save.
Moments later the Australian was again in the thick of the action with a shot on the turn, but Given, quite a distance off his line, was alert to the danger.
After twice knocking on the door, they would finally get the goal their improvement deserved, but like the goals City scored, it was down to defensive errors more than good attacking play.
Shay Given nonchalantly played the ball to Vincent Kompany, who was robbed of the ball by Morten Gamst Pedersen and the Norwegian took full advantage by curling the ball into the corner of the net.
It was the first goal conceded under the Roberto Mancini era, though it was little consolation for Rovers.
But for just a moment, Rovers had the home side rocking. Junior Hoilett drilled an effort across goal, Pedersen headed wide, whilst Garrido and Kompany were uncharacteristically nervous at the back.
As the fourth official showed the number three, it turned into the number of goals scored by Carlos Tevez, but again it was poor play by Rovers as they wasted possession in the own half to allow Robinho to find his fellow South American, and has had been shown twice in the game, he needed no second invitation and he curled the ball past Robinson.
With a Carling Cup semi-final on Thursday night, the game couldn't have ended much worse for Rovers as both Gael Givet and Steven Nzonzi didn't finish the game as they accidentally clashed heads.
Both Frenchman, plus Benni McCarthy who was injured in the warm-up, must now be considered serious doubts for the first leg at Ewood.
MAN CITY: Given (c), Richards, Zabaleta, Garrido, Petrov (sub Boyata 87 mins), Barry, Benjani (sub Santa Cruz 81 mins), Tevez, Kompany, de Jong, Bellamy (sub Robinho 69 mins).
Subs not used: Taylor (GK), Wright-Phillips, Sylvinho, Ibrahim.
ROVERS: Robinson, Jacobsen, Samba, Nelsen (c), Givet, Emerton, Andrews (sub Hoilett 46 mins), Nzonzi, Pedersen, Dunn (sub Olsson 66 mins), Di Santo (sub Kalinić 46 mins).
Subs not used: Brown (GK), Reid, Olsson, Salgado, Chimbonda.
Booked: Zabaleta (Man City), Pedersen (Rovers).