Bad news, but news that in all probability could have been far worse.
In his weekly press conference yesterday, Manuel Pellegrini confirmed the prognosis that Aguero was likely out until the end of February. Per The Guardian:
"Maybe one month but we are not sure now," said the manager, who attempted to shrug off Agüero's absence.
"Yes, of course [it will be difficult] because he is a top player for us but I think we will replace him; we hope we can continuing doing. Sergio [was] just coming back from a [calf] injury when he could not play for a month and all the other strikers replaced him, so I hope they continue the same way.
"He's a very important player for us because he's a top player. There's no doubt about that but we've just played one month, or five weeks, without him and we've continued winning and we've continued scoring goals."
Pellegrini is correct of course in that the goalscoring form (or indeed points return) showed no sign of slowing during Aguero's recent absence. However, City face games against Chelsea (in both the Premier League and FA Cup), The Capital One Cup final and the first leg of the Champions League tie against Barcelona, games in which the difference making qualities of Aguero could be needed to sway tight encounters.
Even if Aguero does return towards the latter stages of February, the second leg in the Nou Camp would be 10 days or so away, a huge risk then to consider him given the few minutes he would have had over the preceeding couple of months or so.
Much will again rest on the shoulders of Alvaro Negredo and Edin Dzeko, with the return to full fitness of Stevan Jovetic proving a timely boost given Aguero's latest setback.
Pellegrini's press conference: