Group F: Borussia Dortmund, Arsenal, Marseille, Napoli This promises to be the tensest group of the lot, with all four sides capable of reaching the knockout rounds. As beaten finalists last term, Dortmund are marginal favourites to outlast their rivals, leveraging last year's experience and the fact that they held onto Robert Lewandowski and secured the signatures of Henrik Mkhitaryan and Pierre Emerick-Aubameyang. Arsenal's swoop for Mesut Ozil has shifted the landscape in Group F, putting Arsene Wenger's men back in serious contention for top spot while Rafael Benitez's Napoli side have made a bright start in Serie A. Marseille, a talented team in their own right, are the outsiders, but their early season form has presented some question marks. Group G: FC Porto, Atletico Madrid, Zenit St. Petersburg, Austria Vienna While Austria Vienna have the unfortunate role of cannon fodder, the rest of this group should be fiercely contested. The bookmakers have installed At...