Mohamed Zidan's Borussia Dortmund slumped to a 2-0 defeat at home to Bayer Leverkusen in their Bundesliga opener on Sunday. Swiss midfielder Tranquillo Barnetta fired the visitors in front after 19 minutes with a low shot from inside the area. Renato Augusto added the second three minutes after a solo effort to give Leverkusen an opening win. Egyptian forward Zidan missed the game as he is still nursing a serious knee injury he sustained last April. The former Mainz, Werder Bremen and Hamburg man is expected to return to action in October. Dortmund thrashed Azerbaijan's Garabagh Agdam 4-0 in the first leg of their Europa League playoff on Thursday.