Cesc being out does hurt them in the middle, but like you said dial squares, Bendtner will play a big role tonight and if he plays like he usually does (missing chance after chance) they could be in for a tough night vs. porto's bend but don't break defense. Arsenal should be pressuring them throughout which also scares me because Porto is very dangerous on the counter attack with Hulk, Falcao, Christian Rodriguez and Raul Miereles... You saw the hard time arsenal had last meeting to contain hulk, and I dont see today being much different. Arsenal should put in a goal or two but Porto will be able to put in one or two themselves on the counter. Arsenal need to score quick to avoid having to bring men up in numbers on the attack, thus leaving themselves vulnerable to the counter. In the end I have to go with Arsenal or nothing in this spot, but it in no way will be a big bet, maybe even no bet at all.
Final Prediction: 2-1 Arsenal (3-1 A.E.T)