The Italian coach guided City to their first league title in 44 years after an incredible last-minute 3-2 victory against QPR on the final day of last season.
But, with his side now three points behind their cross-city rivals ahead of their upcoming encounter on Sunday, Mancini believes the advantage is firmly with Sir Alex Ferguson’s men.
"They are favourites for the title," Mancini told reporters "They were a strong team and they bought [Robin] Van Persie, [Shinji] Kagawa. They added to their squad with another player who scored 25 goals [last season]."
However, when asked whether he had any regrets about not signing Van Persie for his own side, the former Inter boss was adamant that events had played out for the best.
"No, it's in the past," Mancini said. "We have good players that are strong enough. If we improve this moment where we are not scoring a lot of goals I am sure that if we continue to work we can improve."
And with the Dutch striker and his team-mates coming to the Etihad Stadium for the first time this season at the weekend, Mancini believes there is more pressure on his side as United have the luxury of a three-point lead.
|THERE WILL BE GOALS|
|9/1||Bet365 are offering odds of 9/1 that there will be six goals or more in the Manchester derby on Sunday|
"We have only been here for two years. They are used to playing these games in the title race for 20 years. They have won everything for 15 years.
"You can't change this in two or three years. You need more time. For this reason they have a small advantage."
Mancini also confirmed that David Silva is in contention to return after missing City’s Champions League tie with Borussia Dortmund during the week due to a hamstring problem.
"We will try with David," Mancini said. "It is a big risk because afterwards we have a lot of games between now and the end of December and we need all the players to recover."
The 49-year-old was also keen to emphasise that the level of pressure on his side to win the title has not increased after their recent Champions League exit.
"No," he insisted. "I am happy with my job in two years here. You can't win all the games, sometimes you can lose.
"You can lose important games like in the Champions League. But this is normal when you're on the top for a long time."