Dortmund endured a frustrating 1-1 draw against Augsburg and Thomas Tuchel felt his side lost the plot.
Ousmane Dembele scored the equaliser for Dortmund early in the second half to ensure BVB finished 2016 without losing at home.
Dortmund are nine points behind the top spot, but a win between Bayern and Leipzig will see the gap widen to 12.
“We started very well and then completely lost the plot,” he told reporters. “Why I do not know.
“We made an incredible number of errors. We are regularly punished and that makes things difficult at times. We need consistency in the competitions.
“I think that the game really reflects the season so far. In almost every game there are phases where we miss things.
“We made some very simple mistakes, bad passes and simple fouls. After we secured the ball, we switched very badly from defence to offence.
“In these 30 minutes of the first half Augsburg scored a goal. The frequency is incredible. I think it’s the seventh game in a row where we had to come back from one goal down.”