The 25-year-old was forced off at half-time against Barcelona last night as he suffered a reoccurrence of a hamstring injury.
Aguero has played just three games since returning from a previous spell on the sidelines.
The Argentine international missed just over a month of Manchester City's season due to injury, which has had a negative effect on the Citizens' title hopes.
Aguero, who is the club's top scorer despite his injury problems, has been ruled out of Manchester City's match against Hull City on Saturday.
And the former Atletico Madrid is also expected to sit out Manchester City's upcoming games against Premier League rivals Manchester United and Arsenal.
News of Aguero's injury will be music to the ears of current Premier League leaders Chelsea.
The Blues are currently nine points ahead of fourth-placed Manchester City, however the Citizens have three games in hand on Jose Mourinho's side.