Milan are at the Nou Camp tonight with the scores locked at 0-0 after the first-leg.
Guardiola said: "Every ball in the air will be Zlatan's - he's taller and stronger than us. We will see what happens after that."
Skipper Carles Puyol also remarked: "He is one of the best strikers in the world, he is very difficult to fight against, but defending is the responsibility of the whole team. We must keep him out of the penalty area and ensure no good passes find him."