Aguero has been side-lined since December 14 when he sustained a calf injury during the 6-3 win over Arsenal in the Premier League.
"Sergio is working as normal with the whole squad and he is in the squad list for tomorrow. We'll see tomorrow if he can play," Pellegrini said.
"Of course he is a very important player for us. It doesn't matter if we are scoring a lot of goals, Sergio will always be an important player and we are very happy that he is back.
"It's very important because we have not only important games coming up, but we have a lot of games also and all of them are important for us because we are for the moment the only team that are in four competitions and we want to continue."