Barcelona's defense is not enough strong. PSG can take advantage of this opportunity. If Mbappe and di Maria play well, they will be able to knock down the Barcelona defense. But if Neymar is in the team, the players are more cheerful and strong mentally. I'm not sure if Mbappe will be able to perform well without Neymar.
My prediction Barcelona will win this first leg. Most likely Neymar will miss the match and there was a rumor that Angel Di Maria and Marco Verratti also won't play the first match because they are both injured while playing against Marseille.
Moreover, this first leg will be held at the Camp Nou and of course, this is an advantage for Barcelona.