Villa will meet PSG in the final eight after their 6-1 aggregate victory over Club Brugge.
"PSG are a very good side but they've changed their philosophy recently, especially under Luis Enrique. They're no longer just spending money on names," Friedel told BBC Radio 5 Live.
"I've known a few managers that haven't had the happiest of times there, off the field and trying to build something at PSG. It seems like they finally listened to the sporting directors, finally listened to the head coaches and changed things. It'll be difficult, man.
"PSG beat a very, very good Liverpool side over two legs. In that first leg, especially if Alisson didn't play so well, the tie could have been dead and buried but Unai Emery is a master tactician - he really is - and he'll try to obviously stop PSG from playing. They're very, very energetic going forward.
"I love the fact that Aston Villa has one of the best goalkeepers in the world (Emi Martinez) as well because he's going to have to make some saves over the two legs, for sure."