Agree, not a big problem for Arsenal, but they have to remain alert to their current condition, when it becomes a full defensive match for Porto, it will be hell for Arsenal. I previously forgot to mention that apart from Otavio, they also have Pepe there, so Arsenal must really solve Porto's solid defensive problem. Remember that Porto only needs a draw here to advance to the next round.
Pepe is old his physical endurance must not be as good as when he was young. against a young Arsenal team playing at home and spartan pepe will definitely drain physical and energy so performance for 90 minutes will definitely not be stable. as long as Arsenal does not concede a goal first or the players do not quickly despair, they can definitely advance to the next round.