And having failed to make the most of a period in which they at times played some crisp, attractive football without really threatening, it was City who almost scored.
Richards superbly connected with Ousmane Dabo's corner and appeared certain to head the home team into the lead.
The ball struck Bentley on the thigh and up on to his arm before a scramble broke out that resulted in another corner for City.
The ball would have gone into the net had it not struck Bentley's arm - but the injury to Ooijer appeared to be of more immediate concern.
He tangled accidentally with Bernardo Corradi and appeared to suffer a serious ankle injury as he trapped his leg under the City player, who had fallen to the ground.
Richard Dunne headed over for City from another corner before Pedersen struck.
Pedersen got the wrong side of Hatern Trabelsi at the far post and headed a superb cross past Nicky Weaver.
Pearce brought on Georgios Samaras and DaMarcus Beasley after the break, replacing Corradi and Trevor Sinclair.
Samaras crafted an opening from nothing with a neat turn and run into the space but could not quite find the target with a shot across goal.
Shabani Nonda was through on goal for Blackburn but appeared to be harshly penalised for a handball, while the Democratic Republic of Congo striker later played Benni McCarthy through but the South African shot wide under pressure.
And it was Rovers who scored the decisive second goal, his brilliant free-kick sailing over the poorly-formed City wall and past Weaver.
City were much improved in the second-half and unlucky not to pull a goal ball when Vassell connected with Beasley's cross but directed the ball straight at Friedel.
Vassell, perhaps City's best player, forced Friedel into action again before the end with a shot on the turn.
Close to full time Rovers substitute Derbyshire slipped Stephen Jordan and beat Weaver from an acute angle to cap an impressive win for the visiting team.
Manchester City manager Stuart Pearce:
"I think Blackburn played much better than we did. We did not deserve anything from the game.
"They passed the ball better than we did and out-thought us. We did not impose our formation on them.
"It is disappointing but we have got to learn from it. There were too many people not at the races and there were no excuses from out point of view."
Blackburn Rovers manager Mark Hughes:
"We are doing fine on our travels at the moment and I am delighted with the manner of the performance, not just the reuslt.
"We dicatated the tempo, we were calm in possession, created chances and took the ones that we needed.
"We looked at the way City shape up and felt there could be joy down the wings and that is how it panned out."
Man City:
Weaver, Richards, Dunne, Distin, Trabelsi (Miller 75), Sinclair (Beasley 46), Ireland, Dabo, Jordan, Vassell, Corradi (Samaras 46).
Subs Not Used: Isaksson, Johnson.
Booked:
Dunne.
Blackburn:
Friedel, Ooijer (Emerton 35), Henchoz, Khizanishvili, McEveley, Bentley, Kerimoglu (Gallagher 84), Savage, Pedersen, Nonda (Derbyshire 78), McCarthy.
Subs Not Used: Enckelman, Peter.
Booked:
Henchoz, Emerton, McEveley.
Goals:
Pedersen 44, 62, Derbyshire 90.
Att:
36,590
Ref:
P Dowd (Staffordshire).
