blackwhitereadallover.com/2017/2/20/14661914/juventus-fc-porto-opposition-profile-2017-champions-league-tactics-formation
This is the best Porto profile and what should we expect from them that I've read online.
I think that Allegri will go and play cautiously, by not starting with both Brazilians in the flanks and by trusting Benatia over Rugani. I also expect that he will think twice before starting Pjanic over Marchisio, because with Pjanic, when we'll attack we'll have at least 5 players forward, risking to get hit by Porto's counters. If Chiellini and Barzagli won't start, I expect this lineup from Allegri:
Buffon
Lichtsteiner - Bonucci - Benatia - Sandro
-------Marchisio-------Khedira-----------
Cuadrado-----Dybala---------Mandzukic
----------Higuain-------------------------
Personally, I'd go with a 4-3-3, considering all the aspects, with something like:
Buffon
Alves---Bonucci---Benatia---Sandro
Khedira----Marchisio---------Pjanic
Dybala-----Higuain--------Mandzukic