Chelsea lost the game 2-1 after Emmanuel Adebayor cancelled out his own goal and Carlos Tevez managed a match-winning free-kick.
But Ancelotti insists there is no reason to worry despite their setback.
He said: “We don’t have any reason to be worried.
“We are doing well at the moment but today it was difficult because Manchester City played very well.
“But we are still top of the league and we have two more points than Manchester United so we do not need anything extra.”
Ancelotti was disappointed with referee Webb as he felt there was a handball by Micah Richards just before Adebayor’s goal.
“We were disappointed with the referee,” Ancelotti said. “I am surprised because I consider Howard Webb to be a fantastic referee but we felt it was a handball by Richards.
“I did feel we deserved to draw, but we lost.”
