The Italian's side welcome rivals United to Eastlands in Sunday's third round clash, but the former Inter manager does not believe the result will affect the championship race
The club face Manchester United in the third-round of the Cup on Sunday at the Etihad Stadium, in a repeat fixture of last year’s semi-final at Wembley, in which the Blues finished victors against the 10-men of United.
Mancini believes their subsequent 1-0 win in the final against Stoke City was pivotal to the club's mentality, as they look to win their first Premier League title this year.
“It was really important for the club,” Mancini said at a press conference on Friday.
“When you build a new team you have to start to win very quickly.
“If you get one cup, in that moment you can understand if you work hard and win the FA Cup, you can win the championship.”
The Italian boss believes United will be keen to bounce back following back-to-back Premier League defeats to Blackburn and Newcastle United, but suggests the outcome of Sunday's game will not have a big impact on the title race.
“The FA Cup is important for us,” Mancini added. “We won it last year and want to go in the final again if it is possible.
“It is a difficult game. It is a derby.
“It is harder because they are angry after two defeats and they are usually very strong after a defeat.
“But it is not important for the Premier League, other than maybe physiologically.”
Mancini also insisted he is not worried with Edin Dzeko’s current dry spell in front of goal, with the Bosnian striker failing to score since early November, over two months ago.
“I am happy with Edin,” he said. “He didn't score against Liverpool [in our last match] but he was really strong.
“He played and worked for the team. This is very important for me.
“I am sure he will start to score very quickly.”