Injuries to Argentina internationals Sergio Aguero and Pablo Zabaleta will test Manchester City's squad depth ahead of a crowded Christmas schedule.Aguero could be out for up to eight weeks, manager Manuel Pellegrini said on Friday, after he suffered a calf injury against Arsenal last weekend while right back Zabaleta pulled up with a hamstring problem in the League Cup on Tuesday.After spending millions building one of the most glittering playing rosters in European football, City will have to dig deep into their reserves ahead of matches against Fulham on Saturday and Liverpool four days later."Aguero could be (out for) eight weeks, could be four. We will see the way he is working, but he is improving every day," Pellegrini said."I am confident that he will come back as soon as he can."I think Pablo is not so big an injury. Maybe he will be back soon. Maybe a week or two, but the doctor will decide. I am not a doctor. Micah Richards, Matija Nastasic and Stevan Jovetic are also out."City have an abundance of strikers to replace Aguero, but with Zabaleta and Richards both ruled out, Pellegrini has a decision to make about who to play at right back.