TV cameras picked up footage of the former Barcelona boss with his arm around the youngster, seemingly giving him instructions on the touchline.
Guardiola has since revealed that it was part of his plan to ramp up the speed of the match, which ended up being a convincing 5-0 win for City at the Etihad Stadium.
"If you analyse 30 minutes in the first half, we were not ready to be there," Sport quotes Guardiola as saying. "Maybe over 90 minutes you cannot be there all the time, but it was slow.
"If there was a foul, no-one went to take the ball and start to play. There was five, ten seconds before someone goes to take the ball and start to play. When this happens everything is slow.
"So the ball boys were slow, everybody was slow. And we have to create in the game, to provoke the game. And we didn't for most of the time in the first half. In the second half, you could see immediately that the team was ready."
City currently sit at the top of the Premier League table on level points with rivals Manchester United.