Don't see the Gunners losing here. I expect them to control the flow of the game and play for at least a tie. Dortumnd have a number of key players out including Reus, Hummels, Sahin, and Gundogan. Arsenal have a slight issue in defense with Debuchy out and Chambers a 50/50 chance to play with tonsillitis. Furthermore Arsenal are missing Giroud who is a nice target man that holds the ball up well but I think Welbeck can step in and provide adequate cover. Sanchez seems to have assimilated quite well and I look for him to step up big on the European stage and increase his tally for Arsenal.
Arsenal +0.5 @ 1.990
Good luck