I don't see Arsenal as part of the contenders in this season title race. Arsenal should first of all, win EPL before they can start chasing the Champions League title. Barcelona isn't showing too much of quality in them this season. Maybe, I am using the few matches that they have played to judge them but they need to improve their performance if they want to be part of the Champions League contender this season.
Season by season Arsenal never favorite team for winning UEFA Champion League, last season kicked out by Bayern Munich at quarter final round and can't remember well when the latest moment Arsenal success qualifying until semifinal or reach final round.
For phase round absolutely Arsenal easily for qualifying but after qualifying to knock out or quarter final round will get difficulty exactly facing the top teams. Still enjoying for other team fans make judge or joke about Arsenal as the top premier league team until nowadays not winning Champion League. Can't acceptable by Arsenal fans after many top player recruit still difficult to be the winner of Champion League.