City failed in their last-minute pursuit of the Chile international on Deadline Day this summer when making two bids for the forward, the latter of which was in the region of £60m.
"He's an Arsenal player. His manager had to speak to him," Guardiola said. "You know the situation - before the transfer window was open, and now it is closed."
"He's an Arsenal player and is so important for them, for his talent that he has, you have to try and control him."