Manchester City boss Manuel Pellegrini has revealed that he does not yet know the severity of Joe Hart's latest injury setback.
The Sky Blues goalkeeper was substituted after 81 minutes of City's 1-0 Champions League defeat by Juventus on Wednesday night.
It initially looked like a hamstring injury, but Pellegrini says that he will not know the full extent until Thursday.
"We'll see, maybe he has a problem with his hamstring," the Chilean manager told BT Sport. "It can be his back that produces that pain.
"At the moment it is impossible to know what he has so we will see tomorrow."
Samir Nasri, David Silva and Vincent Kompany are already sidelined for Pellegrini and co this season.
