Manchester City captain Vincent Kompany will be out of action for at least a month with a groin injury.
Kompany, 27, limped off during City's 4-0 Premier League win over Newcastle United on Monday.
Manager Manuel Pellegrini said: "I prefer the doctor to say the last word, but I think at least one month."
Kompany is expected to miss City's next two matches against Cardiff and Hull and is a doubt for Belgium's World Cup qualifiers in September.
Fellow centre-back Matija Nastasic missed the Newcastle game with an ankle injury, forcing Pellegrini to use Spanish midfielder Javi Garcia as Joleon Lescott's partner in central defence for the final 19 minutes.
However, Nastasic returned to training this week.
Pellegrini said: "Nastasic is working normally with the squad and we will see if he starts (against Cardiff on Sunday)."
The summer transfer of Kolo Toure to Liverpool has reduced the central defensive options available to Pellegrini, but Micah Richards and Dedryck Boyata remain available for selection.