The Italian has revealed that the Argentina international has picked up a "stupid injury" to his foot but was reluctant to go into details on the specific diagnosis of the striker's problem.
"It was not his fault but he can't play with this injury for one day, 10 days or two weeks. I don't know," said Mancini.
"I prefer not to say [what the injury is]. But he couldn't play against Stoke and can't play tomorrow. I hope he can recover for Arsenal next weekend."
With Aguero expected to be sidelined for a period of time, Mancini may be forced to call on controversial frontman Carlos Tevez.