City's fierce rivals currently sit nine points clear at the top of the table but Mancini is clinging onto hopes that his side can replicate last season's comeback from an eight-point deficit to win the league title.
"The season is long," BBC Sport quotes Mancini as saying. "Nine points today could be nothing. With 13 games to play it's important we believe and continue to try and win all of our games.
"Maybe we won't win 13. United were better than us until now and have nine points more, but in three months everything can change like last year."
City will continue their campaign with a trip to Southampton tomorrow.