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Manchester City boss Manuel Pellegrini fears Samir Nasri could miss most of the rest of the season, but hopes Vincent Kompany and David Silva are back in action within a week.
French forward Nasri, who has missed City's last six games with a hamstring injury, this week revealed via Twitter that he could be out for another three months.
Now Pellegrini has given more details about the 28-year-old's condition, revealing that he faces a tendon operation after suffering a setback on the training ground, and the lay-off could be longer than feared.
Pellegrini said: "We don't have Samir Nasri for four or five months. He has a tendon injury in his right leg so now he must have surgery because it's an important (serious) injury."
Spain playmaker Silva remains on the sidelines with the ankle injury suffered while on international duty in October. Pellegrini has claimed on a number of occasions during his lay-off that he is close to a comeback, but he is still frustratingly short of fitness.
Pellegrini said: "It's a long injury because it's not a muscle injury. It's an ankle and for different reasons he can't be 100 per cent fit.
"If a player is not comfortable I think that he can't play. I hope it's the same as with Vincent, that next week he can be okay."
Influential captain and defender Kompany is out with another calf injury just over a month after returning from a five-game lay-off - and becoming the subject of a club-versus-country row over his fitness - with a similar problem. His latest calf injury is his 11th such problem since the start of the 2011-12 season, while there have also been absences for groin and hamstring problems in that time.
Pellegrini said: "The calf is such a difficult muscle you never know how much (time) he needs but I hope that by next week he will be okay."
The good news for City this weekend is the return of leading striker Sergio Aguero, who has recovered from the hamstring injury that has kept him out for seven games since scoring five against Newcastle in October.
Pellegrini might have wished to ease the 27-year-old back into action but with Wilfried Bony now out with a hamstring problem, the Argentinian is set to line up against Liverpool in Saturday's Barclays Premier League clash at the Etihad Stadium.
Pellegrini said: "It will be difficult because he has gone so many days without playing and I don't think he is ready to play 90 minutes or to play two or three games in a week. It is important for Sergio to evaluate during the game how many minutes he feels he can play.
"But he must start in this game because we don't have Bony and it is important for the team to have Sergio."