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.
I did not watch the match, but looking at the match statistic, Arsenal did not even make a single shot on goals out of 7 attempts. There must be something wrong with the attacking players and it should be evaluated especially for the 2nd leg. Although Arsenal will play as the home team on the 2nd leg but it is not a guarantee that they will win easily against Porto. Porto can be more motivated to win because they are underdog, pressure is on Arsenal so they need to overcome the pressure especially their fanatic fans will be expecting them to win and qualify for the next stage.