Jo, the only senior striker in the team, rose to the challenge to cancel out the opening goal from Niccolo Giannetti.
The Brazilian kept a cool head in the 77th minute to sweep the ball home at the back post following a cross from Adam Johnson.
City manager Roberto Mancini made nine changes to his side, with only Jerome Boateng and Jo retaining their places following the Barclays Premier League victory over West Ham at the weekend. Micah Richards was given the captain's armband.
Mancini saw City go behind in the 43rd minute with a goal out of nothing. Del Piero delivered a cross to the back post and Giannetti steered it home after getting to the ball before Boyata.
But City created enough chances to have won it with Johnson, Milner and Jo all going close.