Former Borussia Dortmund coach Matthias Sammer has described the club's players as "immature" after their shock 2-1 Bundesliga defeat to Augsburg on Friday.

The loss means reigning champions Bayern Munich can move level on points with Dortmund at the league summit if they beat Borussia Monchengladbach on Saturday.

Lucien Favre's side have now won just once in their last five games and Sammer has warned Dortmund's players that they need to change their mentality swiftly if they are to win a first Bundesliga title since 2012.

"Because they have already been German champions, there are expectations on Dortmund," the 51-year-old told Eurosport.

"But they are immature. The game was decided in the head. You have seen for a while now that they do not know what to expect.

"In these games they do not behave like a champion, but like an average team in the Bundesliga."

The club's sporting director Michael Zorc, meanwhile, bemoaned Dortmund's inability to match Augsburg's "enthusiasm and passion".

"When we lose, it is clear that we are not satisfied and very disappointed," he told reporters.

"They brought extreme enthusiasm, passion and willingness to run on the pitch. You could see that they wanted to win and forced us into too many mistakes.

"We did them a favour by making too many simple mistakes on the goals that we conceded."