Manchester City captain Vincent Kompany is likely to be sidelined for a month with a groin injury, manager Manuel Pellegrini has said.The influential defender limped off during the second half of City's season-opening Premier League win over Newcastle on Monday.The 27-year-old will miss City's next two matches against Cardiff and Hull and is also likely to be unavailable for Belgium's World Cup qualifiers in September.Pellegrini said: "I prefer the doctor to say the last word, but I think (he will be out for) at least one month. The doctor can give more information."Kompany's absence leaves Pellegrini hoping fellow central Matija Nastasic, who suffered an ankle injury last month, will be fit to return at Cardiff.Nastasic was expected to miss the first month of the season but returned to training this week.Pellegrini said: "We will see. Nastasic is working normally with the squad and we will see if he starts."