Dortmund were beaten 2-1 at home to Werder Bremen – who had not won away in the Bundesliga since April – on Saturday and now stand 13 points behind league leaders Bayern Munich.
Goals from Maximilian Eggestein and Theodor Gebre Selassie either side of Pierre-Emerick Aubameyang's equaliser piled further pressure on Bosz, with Dortmund having won just once in their last 13 matches in all competitions, against minnows Magdeburg in the DFB-Pokal.
And Bosz, who took charge in July after leading Ajax to the Europa League final last season, suggested he would not be surprised if he was dismissed before seventh-placed Dortmund's next game at Mainz on Tuesday.