Vincent Kompany has been ruled out of Manchester City's Premier League clash at Chelsea on Sunday.
The City captain has missed their last two games with a thigh injury and manager Manuel Pellegrini, who did not take him to Russia for Wednesday's Champions League win over CSKA Moscow, had hoped he would be able to return for the clash at Stamford Bridge.
But the Belgian defender will not recover in time, with Pellegrini saying: "Vincent is still injured. He will not have a chance to play."
Midfielder Javi Garcia has deputised for Kompany in defence for the last two games but summer signing Martin Demichelis is also fit after a hamstring injury and could make a belated debut following his four million pound move from Atletico Madrid.
Jack Rodwell, who has only made one first-team appearance this season, is also back in contention.
And manager Pellegrini believes the in-form forward is one of the top five footballers on the planet.
He said: "I always talk with Sergio [and tell him] that he for me is one of the five top players in the world and he must try to demonstrate it in every game he plays. He is playing with more intensity when we don't have the ball. He has a lot of quality to make the difference."
But Pellegrini deflected the credit for Aguero's fine form, explaining: "He was an important player also in the past. With his goal Manchester City won the title [in 2012]. We hope in the future he will continue being a very important player for the club."