TheSteezyKoalaBarca were in poor form for their standards though and form does matter. They also won 3-1 in the return leg. Veratti is also one of the Parisian's more important player, and if I'm correct Marquinhos will have to play at RB as Aurier is out, so it may be tough for him to play out of position against Neymar of all people. It's not a cakewalk by any means but Barcelona should have it in the bag.
I have no insight in Blanc's tactics, Marquinhos is pretty comfortabel as a right back, he played that way in Roma quite frequently as well. Or they could go for van der Wiel if they want some attacking prowess, but I'll doubt it since having him on is more like an extra winger. He does have the speed though.
Motta is actually more instrumental to PSG's play, Veratti presses forward but does it al under Motta's lead, who's just a solid consistent rock, never making mistakes. A Pirlo without the panache and mystery, he's quite underrated really.
Still all speculation really, as much as the Cavani/Di Maria swap, I could actually see that happen, Cavani has been good at PSG but not stellar.