With the clock ticking in the third minute of added-time, City were bracing themselves for only one point that would have severely damaged their chances of making the knockout round, when Aguero slid the ball home with the last kick of the game.
City manager Roberto Mancini, stunned when the visitors had taken a fourth-minute lead through Cani, had watched his side pull back through a Carlos Marchena own goal before the break and waste numerous opportunities throughout the game.
"I hope that it will be very important, this goal," the Italian told a news conference. "Everything can happen in this group, also for the first place."
The visitors silenced the home crowd in the fourth minute when City keeper Joe Hart could only parry Giuseppe Rossi's shot, sending the ball to the feet of Cani who slid it home.
The late arrivals glanced at the scoreboard on the way to their seats tutting in disbelief that the Champions League adventure could soon be over and then watched as City's chances poured in as heavily as the rain.
Aleksandar Kolarov's goal-bound free-kick midway through the first half was tipped over the bar by Diego Lopez, while Nigel de Jong went close with a long-range effort and Yaya Toure squandered a good opportunity.
Mancini's decision to bring on holding midfielder Gareth Barry for Adam Johnson in the 40th minute stabilised City and allowed Toure to get further forward and they made it count soon afterwards.
"I think in the Champio
