Pep Guardiola says Sergio Aguero will be out for "a few weeks" after picking up an injury during Manchester City's win against Chelsea at the weekend.
The nature of the injury was not made clear by Guardiola in his pre-match press conference for their midweek Champions League game, but he confirmed Aguero would be out for a few games.
That timescale would appear to rule him out of the Manchester derby against United, which takes place on December 7, and even Guardiola admitted that it would be a miracle if Aguero recovered in time.
The Argentinian limped out of Saturday's 2-1 win against Chelsea, and he will definitely miss Tuesday night's Champions League clash with Shakhtar Donetsk, but his return date is unknown.
"Sergio will be out for a few games, a few weeks. I don't know exactly," said Guardiola. "(The injury) is at the front."
Asked about the United game, the Spaniard added: "Maybe we will have a miracle but I don't think so."
City will qualify for the last 16 of the Champions League if they avoid defeat against Shakhtar, and Guardiola added: "The position we have is good but we have not qualified yet.
"Tomorrow is a chance."
Jesus to step in for Aguero
Gabriel Jesus will be the man to step into Aguero's shoes up front, and the Brazilian added: "I am not happy Sergio is injured.
"I don't like it when my friends are injured, but every day I work hard and I am ready."
Guardiola's assistant Mikel Arteta has been linked with the Arsenal job should Unai Emery leave, while Everton could also be in the hunt if Marco Silva is sacked.
Guardiola backed his fellow Spaniard to be a successful manager when it happens, saying: "For sure he will be a manager.
"I want him to stay here as long as possible but personal life is personal life, professional desire is professional."
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