The reigning champions are preparing for their Premier League title defence which kicks off on August 19 at home against top flight newcomers Southampton but Mancini has revealed there is still some way to go in having his squad in tip top shape.
"The (recent pre-season) games against Oldham and Limerick were very important, but I think we need another three or four weeks for these players to get back to full fitness," Mancini told the club's official website ahead of Sunday's Community Shield against Chelsea.
"We will all need to work very hard at Carrington. We will start to work together, the whole team together as we prepare for the season ahead.
"For us it was important that the players play in the European Championship, but they needed a month to recover because last season was very hard and this season will be very long."