Striker Sergio Aguero has been forced to withdraw from international action with Argentina because of a calf injury.
The South American nation have World Cup qualifying fixtures with both Uruguay and Venezuela coming up at the start of September, but the in-form forward will spend the break from club action in the treatment room.
During the closing stages of City's 3-1 victory over West Ham United on Sunday afternoon, the 28-year-old picked up a knock and was substituted by boss Pep Guardiola.
It has now emerged that the issue is serious enough to sideline him for at least the next 10 days and potentially the Manchester derby, which is scheduled to take place after the international break.
Regardless of his fitness, he could still miss the match through suspension if the Football Association decides to take retrospective action for what appeared to be an elbow on Winston Reid at the weekend.
