Aguero came off 13 minutes from the end of Saturday’s Premier League win over Chelsea with a thigh injury.
Speaking at his pre-match press conference ahead of Tuesday’s latest Champions League group game against Shakhtar Donetsk, the manager revealed he expected our top scorer to be out for ‘a few games’
And he confirmed that he expected our all-time record scorer to miss the Etihad derby with Manchester United on December 7th.
“(Sergio will be out for) a few games - I don’t know exactly,” said Guardiola.
“It will be a few weeks, exactly how many I don’t know.
“He has a tendon problem in front –so it will be a few games out.
"(Will he be fit for) the derby?I don’t think so, maybe we have a miracle but I don’t think so.
"We will miss Sergio, we have had some problems with injuries but we will wait for him and meanwhile we have Gab and Sterling who can play in that position. We will live without him for a while.
“There are no other injuries. David (Silva) had cramp (on Saturday) but he’s okay.”
But the manager insisted they would not be used as an excuse and lauded the quality available throughout the rest of the squad.
"Of course, its toughest period coming now with a lot of games in December, January, February," Guardiola added.
"It is what it is so we would prefer to have everyone but my advice to players is don’t think too much.
“Don’t think about massage room and see which players we have. We have enough good players and quality, mentality will give us an extra and maybe help us.
“Prepare for tomorrow as best as possible and get Champions League (qualification) in the pocket for February.
“I tell them (the players) injuries are no excuse form day one. We never say that, I am sorry for them and we will wait for them but that is why we are a good squad.
“The best thing is to move forward. Nobody cares about if you have injuries, it is important to find solutions with what we have."
With 10 points from our first four group games, City need just a point to ensure qualification for the last 16 tomorrow night.
And on the back of last Saturday's superb 2-1 win over Chelsea, the boss said he was anxious for his players to see the job through
"The position we have is good but we have not qualified," the boss added.
"Tomorrow is a chance, Shakhtar know us quite well. We come back after a demanding game against Chelsea and will see tomorrow how our conditions is physically.
"We have to do our best to go to Zagreb (for next month's final group game) with the job done."