Lucien Favre held nothing back when assessing Borussia Dortmund's performance after a humiliating 5-1 home loss to Stuttgart on Sunday (AEDT).
The stunning result means Dortmund have now suffered three straight defeats at home in the Bundesliga for the first time since the 2013-14 season, when Jurgen Klopp was in charge.
Favre's future will come under scrutiny following this latest setback, despite steering BVB through to the last-16 stage of the Champions League.
The Swiss coach admitted his side - without the injured Erling Haaland - were masters of their own downfall, branding the display "very, very bad" while also praising their opponents.
"That was a disaster. It was bad," Favre told the media after the game.
"We weren't good at winning the ball. We made too many big mistakes. That's hard to explain. If you are not good at winning the ball, I mean the whole team, then you have a problem.
"Stuttgart played well, but we were very, very bad. That will not do. Stuttgart played well in the first half, but we made it 1-1.
"Still, we wanted to do better in the second half. We gave up a very stupid goal. That worried the team. We weren't there today. "
Dortmund had only lost one of the previous 16 league meetings between the teams, while they were on a 13-game unbeaten run at home against promoted sides.
However, Stuttgart had not lost on the road since returning to the top tier, a run that now stands at six matches after they demolished their opponents at Signal Iduna Park.
Silas Wamangituka scored twice, his brace sandwiching an equaliser from Giovanni Reyna, before Stuttgart pulled clear with two goals in three minutes, Philipp Forster and Tanguy Coulibaly on target. Substitute Nicolas Gonzalez then added a fifth in added time.
Captain Marco Reus accepted the result is unacceptable for Dortmund, who have now won only six of their 11 league games this term, leaving them outside the top four in the table.
"Stuttgart showed us how we actually wanted to play," Reus said. "They were aggressive. They were very compact, switched over when they lost the ball and played great together at the front.
"It's not a coincidence. We just missed everything we really need on the pitch. It's a very, very difficult evening.
"We have to digest it first. We are not allowed to present ourselves like that. We have to talk about it and report the errors."
Dortmund have little time to reflect, though, as they are back in action on Tuesday, when they travel to Werder Bremen in Bundesliga action.