It's an incalculable loss and seeing Martinelli's role as a left winger is so important, it will make it more difficult for Arsenal to penetrate from the left side of the opponent's defense. However, Mikel Arteta doesn't need to be confused because he still has Trossard to replace Martinelli and the Belgian player is actually quite good. But Trossard is more often used by Mikel Arteta as a supersub and seeing him possibly playing as a starter makes me doubt whether he can make a difference or not.

The problem for Arsenal is how they will be able to get past Porto's strong defense, especially since there is an experienced defender in this competition, namely Pepe. Even though he is 40 years old, his role as controller of Porto's defense in the first leg repeatedly succeeded in thwarting Arsenal's attacks. It will be very difficult if this main job cannot be completed and it is possible that if Arsenal is still deadlocked, then Porto will maximize this aggregate advantage and Arsenal could go home sooner.