Borussia Dortmund manager Jurgen Klopp has taken the blame for his side's 2-0 defeat to Bayer Leverkusen on Saturday.
A goal in the ninth second from Karim Bellarabi and a late strike from Stefan Kiessling ensured that Dortmund started their Bundesliga campaign on a losing note.
"The start to the game hurt, of course, Leverkusen used their plan; we, unfortunately, did not," he told reporters. "We have a lot of work to do. That we were not awake at the beginning I blame on myself.
"Our feeling in the first 25 minutes was influenced dramatically after the early goal. The team has shown great will and if we'd taken one of our chances, then we would have turned the game. But Bayer earned their win."
Dortmund finished second in the league last season and were runners up in the German Cup final.