Manchester City boss Manuel Pellegrini is unsure about the extent of Sergio Aguero's hamstring injury.
Aguero was substituted at half-time in the midweek Champions League clash with Barcelona.
"Tomorrow, we will know exactly the extent of Aguero's injury," Pellegrini asserted. "We do not know exactly what is wrong. He will be out for more than one week but I don't think it is very serious.
"I hope that he will only be out for a couple of weeks."