Manuel Pellegrini's side finds itself in the FA Cup quarterfinals, the Capital One Cup final and the Champions League last-16 stage within the next month, plus a yet-to-be-arranged Premier League clash with Sunderland.
"What affects the Premier League is the change of the fixtures," Mourinho told reporters. "City play later after the other teams fighting for the title play, so it is easier. They know somebody lost, somebody won, they lost two points, one point is enough for us. That is obviously an advantage.
"But it's not their fault. It's the weather, the fixtures, the FA, the Premier League, so it's not their fault."
When asked if Chelsea could win its games to reverse the pressure on to City, he replied: "Leave us in peace. It's not for us. We have to try to win the next game and it's not our fight."
City's increased schedule comes following a 2-0 win over Mourinho's Chelsea in the FA Cup, and the Portuguese acknowledged playing Pellegrini's men just 12 days after beating them was a challenge.
"It's always difficult to play two matches in a row against the same team," he said. "It's very difficult for a team to win consecutively the two matches. You come in at the top of your game, the top of your concentration, the top of your intensity and you win the game. For the winner it's difficult to be back where he reached the top and the loser has time to assimilate the defeat and to create a certain spirit."