Champions League finalists Borussia Dortmund embark on their third consecutive European campaign on Wednesday at Napoli fully aware they are no longer dark horses in the competition. Just 116 days after losing to Bayern Munich in May at Wembley, Germany\'s Dortmund are at Italian league leaders Napoli aiming to prove their run to the final was no fluke. Jurgen Klopp\'s Dortmund are top of the Bundesliga, two points clear of Bayern, after winning their opening five matches and ran riot at home with a 6-2 drubbing of Hamburg on Saturday. Borussia went into last season\'s campaign as something of an unknown quantity before posting wins over Real Madrid, Ajax and Manchester City, but are one of the favourites this time around. \"It will certainly be more difficult than it was last season,\" admitted Dortmund CEO Hans-Joachim Watzke, with Dortmund having also drawn Arsenal and Olympique Marseille in Group F. \"But this is a great opportunity to prove how much we have evolved.\" Despite losing Germany star Mario Goetze to rivals Bayern in July, Dortmund\'s recruitment has bolstered their attacking prowess. Fleet-footed Gabon forward Pierre-Emerick Aubameyang has been signed from French Cup holders St Etienne, while central midfielder Henrikh Mkhitaryan joined from Shakhtar Donetsk. Both scored in the win over Hamburg, but Germany winger Marco Reus has said the defence can not afford to leak more goals. \"In the Champions League, every mistake is punished immediately,\" warned Reus after Dortmund last won the title in 1997. Striker Robert Lewandowski, who became the first player to score four goals in a Champions League semi-final last season in the 4-1 first-leg win over Real Madrid, is eager to start. \"Now the season really starts for me,\" he told magazine Kicker. \"We want to do the same as we did last season -- or even better,\" before adding it was a \"highlight\" to open their campaign at Rafael Benitez\'s Napoli. Source: AFP