City will first bid to get their Barclays Premier League title bid back on track after two games without a win as they host Sunderland in midweek.
They then tackle rivals Chelsea in the FA Cup fifth round on Saturday before the first leg of their glamorous Champions League last 16 tie against Barcelona next Tuesday. Those two games are also both at the Etihad Stadium.
Pellegrini said: "I don't think the season will finish this week but I think it is a very important week for us.
"We have to play in the three competitions and maybe we are not in our best moment for the amount of players that are injured.
"We will see what happens this week, (if) the team returns to normal performance and I hope the future will look better when we have all the players back."
City are currently without the key trio of top scorer Sergio Aguero, midfielder Fernandinho and playmaker Samir Nasri due to injury.
Their absences were noticeable as City were beaten last week by Chelsea in a crucial game in the title race and then as they played out a goalless draw at Norwich on Saturday.
All remain on the sidelines for the visit of Sunderland, who will also be City's opponents in next month's Capital One Cup final and have already beaten them at the Stadium of Light this season.
Pellegrini does not believe City's title chances have been badly damaged because he has been predicting a close fight all season.
He said: "I think it is normal, all teams will drop points.
"It is very important for us, from the last 30 points that we won 25. It is an important amount of points.
"We lost to Chelsea and drew against Norwich but I think that all the teams in relegation positions or bad positions of the table will add points in the second half, so, for me, it is normal.
"In the Premier League, we have a very important three points (against Sunderland), but after that we have 36 points more (to play for).
"I am absolutely sure the Premier League will be decided in the last two games.
"The character of all the squad will be (tested) from now until the end of the season. The team with a strong mind is the team that will win."
City's free-flowing attacking style has earned much praise this season and yielded 115 goals.
The last two games have seen the output halted, but Pellegrini is hopeful the goals will soon start flowing again.
He said: "I am not concerned. In these two games, (Alvaro) Negredo was not 100 per cent, (Edin) Dzeko was not 100 per cent and Aguero was not available.
"I suppose in the future, we will continue to score goals. I hope we will continue doing it but it is not easy.
"On Wednesday we have a match with a good team that are playing well in the last five or six games.
"I am absolutely sure we will have to play a very good game if we want to win."