Dortmund are now without a win in eight Bundesliga matches having gone down to Werder, who were second-bottom at the start of the match, thanks to goals from Maximilian Eggestein and Theodor Gebre Selassie either side of the interval.
Although Pierre-Emerick Aubameyang equalised to become the record African goalscorer in Bundesliga history, it was the latest in a long line of miserable Dortmund performances under coach Peter Bosz.
And Schmelzer did not hold back in his criticism of Dortmund's display as they slipped 13 points behind reigning champions and league leaders Bayern Munich.
"This performance is a joke from us players," Schmelzer told Sky.
"And I've been saying for weeks that we cannot always just talk, but act. Then we play like that, that's amazing.
"I stand here every time and people probably think: he says the same thing over and over again.
"I do not understand how such a thing can happen in such a game. That was really s**t."
Schmelzer was asked directly whether Bosz, whose side won six of their first seven league games in a flying start to his reign, should remain in charge of the team.
"We can talk about the performance," said the left-back.
"A few of the players have sworn in the dressing room, otherwise there was not much talk."