Thomas Tuchel said Borussia Dortmund's performance deserved to be punished, after losing 3-1 to Hamburg.
Goals from Pierre Lasogga, Lewis Holtby and an own goal from Mats Hummels lifted Hamburg into a commanding position at the Volksparkstadion before Pierre-Emerick Aubameyang netted a late consolation on Friday.
Dortmund - five points behind Bundesliga leaders Bayern Munich in second position - had won their previous seven matches and a furious head coach Tuchel slammed his team's display in the surprise defeat.
"The first half was dramatically different to how we want to play, what we demand of ourselves," he told Dein Sky Sports. "We deserved to be punished.
"We started carelessly. With this body language, this performance, we won't win anything anywhere."
Dortmund full-back Marcel Schmeltzer agreed with his manager's assessment, acknowledging the team did not perform to their typical standard.
"It was a lesson," he said. "If you are not 100 per cent, you can't win in the Bundesliga."