The Argentine was expected to be out for several weeks after picking up a hamstring injury in the New Year's Day win over Stoke.
Mancini said: "Sergio is not available for Sunday. We don't want to take a risk. He continues to have treatment this week. I hope he can play against Fulham next game.
"If Arsenal was the last game (of the season), okay, but like this it is impossible.
"Sergio is out for one game but this doesn't change (anything) because we have another three strikers.
"We can change our system any moment, not because we are missing Sergio or other players."
Mancini again stressed that he had no intention of selling Mario Balotelli, who played for City's U21s on Monday and scored two goals in a friendly against Blackburn this week.
"No, it is not true. I am very, very happy with Mario," the City manager added. "He has trained well this week and I hope this year will be different."
City travel to Arsenal on Sunday for the Sky Live clash and Mancini maintains his side are improving as they strive to close the gap on Manchester United.
"We are missing a number of important players but we can go there and come away with a good result," he said.
"We are seven points behind United at present but I don't feel we deserve to be so many points behind.
"Our strikers have been coming back into form again and scoring goals and we will need them to keep doing that.
"Sometimes you go through a period when you don't score so many but we have scored 10 in our last three games so things are improving."
Arsenal v Manchester City is live on Sky Sports 1 this Sunday. For more details click here