I really understand that Porto's defense is very strong. At least Mikel Arteta can find a gap to score a goal in the second leg to advance to the next round. Even though Porto is in third place in the Portuguese League, that cannot be a benchmark for measuring the strength of a club. However, here you can see or find out who will be lucky in the second leg, hopefully Mikel Arteta can find Porto's weak points so they can win or turn things around.
I don't want to believe Arsenal will be playing an easy game against Porto because they will be having the home advantage this time around because even Porto aswell is very much aware of the fact that they both have close to very equal chance at qualification unto the next stage of the league but then Porto seem a step ahead only that if Arsenal gets a miracle enough to stay ahead of Porto without a goal then they can be quiet sure that Porto would've be a stumbling block for their qualifications unto the next stage of the champions league. The solidness of Porto's defence Line is something Mikel arteta needs to study so well and proferre a possible solution to breaking the defense line of Porto before the kick off of their next fixture.
Most persons seem to ignore the fact that Porto has got an unseeming advantage in the fact that they won at their home even if it's by a goal and if they area able to get another against Arsenal in the Emirates than it will mean the gunners will need Three goals to stay ahead of Porto which is look like it's not going to be all that easy and a draw wouldn't keep the gunners in a safe position either, so the gunners have got a whole lot of work to do.
Even though Porto will play as a guest in the second leg, but with the win they got in the first leg, it will be an advantage for them. So they will most likely tend to play defensive football to maintain their advantage. It's definitely not an easy task because the opponent is Arsenal, who will be playing at home and is in an on-fire condition. But still, this match will be quite difficult to predict who will be the winner because I think both teams will definitely play with all their might, and most likely the match will run with high tension which will probably result in a lot of fouls from both sides.