A 3-2 derby defeat at the Etihad Stadium on Sunday has left City six points adrift of their neighbours approaching the busy festive period.
City proved last season they cannot be underestimated, as they snatched the crown in the most dramatic of circumstances, but United are determined to ensure history does not repeat itself.
Mancini is aware his side face a tough task in their efforts to mount a successful defence of their title, but feels City are still the best side in England, regardless of what the standings may suggest.
He said: "Things aren't going well but I know we will still have a great year.
"United have more experience but we have a much better team and play much better football.
"Six points is not a big difference with 24 games still to play.
"We need to try and win five or six games in a row to try and reduce the gap."
Mancini added: "Even though we lost on Sunday, we showed we are a really strong team and can win the title again.
"We were unlucky. We dominated long spells of that game and did not deserve to lose.
"The Premier League is the best campaign in the world at the moment and as we know from winning last year, you can lose a game in the last second."
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