I'm wondering what Arsenal will do as of this stage in the Champions League. They had a successful group stage as expected. Now I can say that they have a comfortable matchup to play against Porto as well. Because I don't believe Porto are one of the teams that can eliminate Arsenal in this tournament. Porto couldn't even beat Barcelona in the group stage. I mean that Barcelona aren't weak of course but I don't think they have played better than Arsenal at all. 
Anyway I see Arsenal in the quarter finals already to tell the truth. But they had better improve their performance more as there is some decline recently.
When Arsenal was drawn against FC Porto in the round of 16 of the UEFA Champions League, I expected Arsenal to win against FC Porto but with the recent performance of Arsenal, I'm not sure if Arsenal could be able to beat FC Porto. If FC Porto can play well in their home, I believe they will beat Arsenal. Anyway I see Arsenal in the quarter finals already to tell the truth. But they had better improve their performance more as there is some decline recently.
Although this moment Arsenal experienced a decline in performance in the Premier League but yes, I personally remain confident that Arsenal will still succeed in beating Porto and Arsenal will be able to qualify for the quarter-finals of the Champions League . But yes, although I am sure Arsenal will qualify for the quarter-finals, but that does not mean Arsenal will be able to easily beat Porto. Because after all, Porto is also not a weak team so it is certain that this match will be very difficult for both teams, and it does not rule out the possibility that Arsenal might also fail. Therefore, the match between Porto v Arsenal I think will be a difficult match too and not easy to predict, although Arsenal have a chance to win but for me the chance is not that big.