I myself did not expect that Arsenal could be defeated by Porto, even though I was very confident with Arteta because in the domestic league they were in a very good game, while Porto underestimated the team a lot because it was based on the popularity of a different league, but Porto could beat Arsenal well. Arsenal will have to beat Porto in the second leg by a bigger score.
Likewise, Barcelona were quite surprising to get a draw against Napoli, but it is true that if only Barcelona draw if they can beat Napoli at home then they will be very sure to qualify for the next round, the second leg is a very important bet.
It's football you have to expect the unexpected, not at all times though, but if you're hardworking and discipline as well precise while attacking, you'd take make good use of chances you get and convert them very well.
Yeah and they also score good numbers lately, ome would think they will do the same to Porto but you know what? Porto is a bigger club when it comes to the Champions League than Arsenal. Arsenal can roam about in the Premier League and Fa Cup but the Champions League Competition has always humbled them.
But then, it seems to be like Arsenal always gets back on to win Porto during the second leg of the games they play. Are we Gon see something like that again?
Nothing to be boggled about, Barcelona are not fine and not having a good season. So whatever you see, you have to take it that way.