Nedum Onuoha is set to be sidelined for up to four weeks after suffering a thigh injury.
The Manchester City defender sustained the problem while in action for the reserves against Wigan and the extent of the damage has now been confirmed.
Manager Mark Hughes does not believe Onuoha will be fit to return until the middle of next month.
"Unfortunately Nedum is injured at the moment," said Hughes.
"He pulled a thigh during the reserves game last week. He played around 55 minutes but felt a bit of discomfort.
"There is a tear in there and he will be out for three or four weeks."
Onuoha signed a new long-term contract over the summer but he has fallen down the pecking order following the arrivals of Joleon Lescott and Kolo Toure.
Roque Santa Cruz, meanwhile, is set to make his first appearance of the season against West Ham next Monday.
The Paraguay international striker will sit out the Carling Cup clash with Fulham as he continues to build up his fitness following a knee operation.
Hughes said: "Roque won't be featuring against Fulham, but the likelihood is that he will play a part in the next game if we can get him involved."