Mancini believes that what City do off the pitch over the next 10 days will be vital to their chances of success.
He has been frustrated that they have been unable to complete the £38million purchase of Atletico Madrid's Sergio Aguero, although the £21m arrival of Samir Nasri has moved a step closer after Wenger relaxed his tough stance on keeping the France midfielder at Arsenal.
Mancini said: "It is important for us to have signed all the new players in the next 10 days if we are to be successful.
"Last year we had four or five important players injured in February and March and our results suffered. This year that cannot happen."