Manchester City breezed past Notts County 5-0 in their FA Cup 5th round replay at Eastlands although he final scoreline was slightly flattering on the host's as three of the goals came in the final six minutes.
"In the first half an hour Notts County played very well," admitted Mancini, who felt the club's Europa League trip to Greece on Tuesday affected their performance.
"It was an important win. I think for us it (the FA Cup) is important. We started the game so slowly because when you play every three days it is difficult to play 100% in every game.
"But after we scored it changed the game. We had more chances in the second half and it was important we scored those goals."