Second-placed City are 15 points behind rivals Manchester United, whom they face at Old Trafford on Monday, and Mancini said last week the title race was over.
"Mario scored 15 goals last season. This is the difference, the goals we did not score," Mancini told a news conference on Friday.
It was Italy striker Balotelli, often in Mancini's bad books for his wild antics, who provided the pass for Sergio Aguero to score in injury time on the final day of last season as City took the title on goal difference from United.
City scored a total of 93 league goals last season. In 30 games so far this campaign they have found the back of the net 55 times compared to 72 at the same stage last season.
"The difference is that we score 20 goals less than last year. Only this difference," said Mancini.
"We concede the same, we have the best defence, we are missing only these goals. We had a lot of injuries, we lost Sergio, we lost Mario," he added in reference to Aguero, who missed the first month of the season and has sustained further knocks.
Mancini again said the title race was finished but felt United's big lead was not a true reflection of the season's form.
"We do not deserve to be 15 points behind Manchester United. They play very well and have won a lot of games and they deserved to stay on top but not by 15 points," he said.
United have won their last seven league matches while City have lost twice and drawn twice in their last seven.
"We want second place. The next two weeks will be very hard and crucial for second place," said the Italian.
Third-placed Tottenham Hotspur, who face City on April 21, are five points back having played a game more while Chelsea are seven behind.
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