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."
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."
Sunderland boss Gus Poyet has warned Manchester City to expect the unexpected as the two clubs prepare to stage a dress rehearsal for next month's Capital One Cup final.
The Black Cats head for the Etihad Stadium on Wednesday evening having slipped back to the fringes of the fight for Barclays Premier League survival following Saturday's 2-0 home defeat by Hull.
Poyet had previously dragged the club into 14th place, as well as a Wembley final, after a vastly-improved run of results, but with their next three league fixtures scheduled to take them to City, Arsenal and Liverpool, their plight could deepen significantly over the next few weeks.
However, they have won three and drawn one of their last four Premier League games away from the Stadium of Light and remarkably, have beaten City on Wearside in each of their last four meetings and for those reasons, the Uruguayan insists they cannot be written off.
He said: "Every time we look at a home fixture, we think we are going to win and we haven't beaten anyone.
"I just try to take them as they come. The idea is to go there and try to get something from this game and something from the Arsenal game and then if we have to go to Liverpool, depending on the cup, the same.
"I don't think we need to analyse too much or give up before we play. We are going to play our game and we will see. You never know.
"We are not a team that you can say you know what is going to happen. We are a quite unexpected team, so we will see."
Poyet knows only too well the weapons opposite number Pellegrini has at his disposal even without the injured Aguero, Fernandinho and Nasri.
However, he has no intention of trying to defend for 90 minutes and hoping for the best against a side which has uncharacteristically failed to score in either of its last two games.
Poyet said: "When I am a fan, I like to see the best players playing. When it's against you, of course not.
"It's not the same - Aguero is one of the best in the world, Fernandinho has been great and Nasri when he starts getting between the lines is a difficult player to play against, so there are plenty of things that mean in this game, maybe we can be lucky.
"That's without talking about the rest of the players they have and what they can do, but it's true that it could be a little bit different because they are not there.
"But I am not just saying it for the sake of saying it - we are going to play to win the game. Then if the opposition is better than you and they batter you and you get a point, you take it and run and go home.
"But the idea is to go and try to perform and see if we can play against them and be a difficult team to play against."
The sides will meet once again on March 2 with the season's first domestic trophy at stake, but Poyet, who will be without suspended defender Wes Brown on Wednesday night following his dismissal at the weekend, does not believe either manager will be able to take too many pointers.
He said: "I don't think so because those players we talked about before are going to be there for the final, for sure.
"But it's true that mentally for the players, it would be good if can get a good result.
"For some reason, it's away from home that we have been doing well, so now it's a big opportunity against one of the top teams."
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