David Silva is expected to be out for three weeks with a knee injury and will miss Sunday's Manchester derby at the Etihad Stadium.
Manchester City's Spanish winger, 28, was hurt in their 2-0 League Cup defeat by Newcastle United on Wednesday.
"Maybe he (Silva) will be out for three weeks so he will not be available," said manager Manuel Pellegrini.
Ivory Coast midfielder Yaya Toure, who also picked up a knock on Wednesday, is expected to be fit.
Pellegrini, whose side lost 2-1 at West Ham United in their last Premier League outing, said: "Yaya has a small problem. We will see him tomorrow - I think he will not have any problem."
The Chilean, whose side are six points behind leaders Chelsea, admitted the loss of playmaker Silva was a blow but believes the reigning champions will cope without him.
"He's a very important player but I always say the same thing - we have the squad and we have to replace him because everyone has different problems with their players," he added.
When asked if he was worried about City's form and if he had considered changing their attacking style, Pellegrini said: "No. I think they (the players) know perfectly what we are doing. I am absolutely sure we will return to our normal performance."