Arsenal was defeated and that is what we call a disaster for the club most especially when the defeat happened to them at home in front of the fans, which could have been a big advantage to them.
Barcelona on the other hand played a 1:1 draw with Napoli and even though Barcelona made the first goal record before the equalization, it still felt better and safer for Barcelona but along the line, they missed their steps and there was an equalization but still, we cant compared the condition to that of Arsenal who was defeated in their game.
I am not worried about Arsenal even though they lost in this match because I'm sure they can win in the second leg with a more score, Arsenal will not waste this opportunity because Arsenal have no choices except the Champions League. I did not underestimate Porto but I thought Arsenal was more worthy to go to next stage and Arsenal will do it in the second leg match.