The Citizens have started the current campaign slowly and are yet to re-produce the same form they showed last season.
City are also struggling in the Champions League, having been held to a 1-1 draw at home to Borussia Dortmund after succumbing to a 3-2 defeat to Real Madrid in the Group D opener.
However, while Mancini accepts there have been problems, he believes the midweek draw with the Bundesliga champions could be the turning point for the season.
"Last year we played well often. This year we probably didn't play like last year, but this is normal because after you win the title the second year is more difficult," the Italian told Sky Sports News.
"The reason is because every game you have pressure because everyone expects you to play like the year before, and sometimes it is not possible.
"We had some problems, but we are sure we can get better. I am not surprised. I was sure it would happen because we changed three or four players, who arrived in the last days of the transfer market.
"It's not a disaster and the point we took against Borussia will be very important."
