PSG's defense aren't weak, but their defenders are shorter than Inter's defenders, which would be a problem if PSG gets aerial attack.
I'm sure PSG already know this and are looking for the right strategy and tactics to beat Inter without aerial attacks. But I hope PSG don't keep defending in the first few minutes. Because I'm sure Inter will put strong pressure on PSG defense. If Inter manage to pressure PSG and successfully score 1 score, I'm sure Inter mentality becomes bigger and there will be a little rough play to reduce PSG mentality.