After the problems of last season, the Argentinian has been restored to prominence at the forefront of City's attack this term. He began the campaign with four goals in as many games but then hit a barren spell and has scored just three since.
Mancini said: "No, I'm not disappointed about this form recently."
He continued: "About Carlos I can say nothing (critical) because when he plays, even if he is not 100 per cent, he's a fighter, he puts everything he can on the pitch, so I can't say anything against him.
"But it is clear that we want our strikers to be scoring goals and at this moment Carlos is not strong and for this reason he was on the bench in the last three games.
"But tomorrow that could change, or in the derby. He's not 100 per cent because he has played many games and that is why at the moment he is not so good."
They then face rivals Manchester United in an eagerly-anticipated derby the following Sunday.
One player Mancini is hoping for more from is playmaker Samir Nasri. The Frenchman has not made a consistent impact since joining City in a £24million move from Arsenal last year. The 25-year-old was also left out of the squad for the midweek trip to Wigan as a precaution against a calf problem.
Mancini said: "In my opinion we are talking about a top, top player here. If he wants he can change every game, but I think he can do better. He has played some good games for us but he can do better because he has everything. I don't think he has struggled."