The prolific Aguero, who has scored 19 goals this season, could be out for up to eight weeks with the calf injury suffered against Arsenal last weekend.
But with his side having 75 goals netted so far this season in all competitions, Pellegrini is not overly worried about having to cope without the influential Argentina star.
He said: "He is a very important player for us but I always say the same when we have a player injured - we have a squad and the squad has to see which is the best team to win every match.
"We will try to replace him in all senses, in scoring and in style."
Alvaro Negredo has also flourished this season, with 13 goals to his name, while Edin Dzeko staked his claim for a regular start with a double in Tuesday's Capital One Cup quarter-final win at Leicester.
Dzeko has had to be content with a place on the bench for many games this season but for Pellegrini the Bosnian has still played a crucial role.
Pellegrini said: "I always try to involve all the players in what we are doing every week.
"After that I must choose 11 starters but all the other players have exactly the same importance and I think Edin Dzeko is working every day very well.
"He couldn't play more because Sergio and Alvaro were scoring goals and the team was playing well but you saw last Tuesday that he played and scores two goals.
"He can play often now. He was always an important player for the team."
Another player Pellegrini is happy with is goalkeeper Costel Pantilimon, who looks set to be return for this weekend's Barclays Premier League trip to Fulham.
England number one Joe Hart, dropped last month, played at Leicester but Pantilimon has done little wrong in a run of seven successive Premier League outings.
Pellegrini said: "I think he is doing okay.
"It was not easy for him to start to play in the Premier League.
"He has played before in the FA Cup but I think he is doing very well.
"It is very important that the goalkeeper is one more player in the team and must be talking all the time. He must be ordering the defence.
"Of course (he does this well), that is why he is in the squad."
City are well placed on all fronts, sitting three points off the top of the Premier League and through to the semi-finals of the League Cup and the last 16 of the Champions League.
They begin their FA Cup challenge next month but Pellegrini is not even considering where it could all end.
He said: "The only target of this season is to win against Fulham.
"If we can do that, then we will see in the next game what we can do.
"There is no future target. It is very important to think about the present, not the future."