Despite his goalscoring record this season and his quality, Haaland did not have much of an impact in either leg for the German side.
City went through to the semi finals after winning 2-1 in Germany on Wednesday, and 4-2 on aggregate.
Guardiola spoke about their plan to stop Haaland getting the ball, as a way to nullify his threat.
He told BT Sport: "I would say this player is almost unstoppable and the best way to defend against these talented players is to not let them have the ball.
"They want the ball, they need the ball, so don't [let them] have it."