Barcelona seem to be very lucky been grouped with Porto, Sharkhtar and Antwerp because clearly they are dominating in the group winning all three first legs and leading with nine points with Porto following behind with 6 points. It doesn’t look like Barcelona will lose even a game in this group, their future in the UCL this season looks very promising.
Even if they lose I don't think it will change anything in general, they can relax in some of the difficult periods and not really care about the group stage match. That doesn't sound like a good idea, but I don't know what will happen by then. The other question is what stage can they get to? Maybe they will fall out already in 1/8, what then?