Son Heung-min's 18th-minute strike was enough for second-place Bayern Leverkusen to inflict Borussia Dortmund's second successive defeat at home in the Bundesliga.
''It was very important to show Germany what we can do,'' said Leverkusen sporting director Rudi Voeller after the 1-0 win. His side has won all three games since losing 5-0 at home to Manchester United in the Champions League.
Former Leverkusen defender Manuel Friedrich's wayward pass from defense was intercepted by Emre Can. Can passed to Gonzalo Castro who fed Son, who rounded Dortmund goalkeeper Roman Weidenfeller and scored from a narrow angle.
Dortmund improved after the break but labored to break down Leverkusen's well-drilled defense.
''We deserved to lose,'' Dortmund winger Kevin Grosskreutz said.
Leverkusen defender Emir Spahic was sent off in the 81st for pushing Henrikh Mkhitaryan in the face. Mkhitaryan took issue with Spahic's heavy challenge on Robert Lewandowski.
Dortmund also finished with 10 men after Sokratis received his second yellow card in injury time, and the side's injury worries increased with both Sven Bender and Nuri Sahin taken to hospital with ankle injuries.
''Both of them could hardly walk. It's hard to tell (the extent of the injuries) but it's not optimal for us,'' Dortmund coach Juergen Klopp said.
