my prediction for Barcelona to not qualify for the next round is still alive, but i have to admit that it's tough right now for Inter to get 2nd place, if they were able to get a draw out of Bayern Munich in Milan there chances could have been way better now, but there is hope still, if they lose against Barcelona it's over, but a draw could make things really interesting.
Barcelona need to win at least two more times in the three remaining matches in the Champions League group stage, as Barcelona are three points behind Inter Milan and 6 points behind Bayern Munich who are currently in first place in Group C. So Barcelona's toughest opponent is Bayern Munich, apart from Inter Milan and for Viktoria I think it will be very easy for Barcelona to handle because Viktoria is not a strong team in Group C this season.
Their fate is in their own hands, namely with the victory in the remaining matches. If they want to be safe then they have to wipe out the rest of the match with a win, that way they will be more comfortable. And the decisive one is the match against Inter Milan, because it will really determine their future steps. Inter also come with the same mission which is to win, otherwise they too will experience the same difficulties.