Augsburg's Ji Dong-won celebrates scoring their second goal with team mates as Dortmund were on the losing side. Photo: Michael Dalder/Reuters

AUGSBURG Bundesliga leaders Borussia Dormund are lacking the maturity needed to be champions, club adviser Matthias Sammer has said following their shock 2-1 defeat at fourth-bottom Augsburg on Friday.

Mistakes in defence led to both Augsburg goals, with South Korean forward Ji Dong Won scoring either side of the break before Paco Alcacer's 81st-minute consolation.

Sammer, who as a player with Dortmund won two Bundesliga title before winning a third as club coach, said young players were making mistakes.

"That's what makes champions  and at 19 or 20 you can't be a champion," Sammer said of the youthful Dortmund squad in comments as TV pundit for Eurosport.

Dortmund were going into games with the public perception they were already champions "but they are immature, they are just immature." The game was not decided on the pitch "but in the head," he said.

"In this sort of game you have to reach 90 or 95 per cent  60 per cent is not enough.

"In games like these against Augsburg, Dusseldorf, Hanover or Nuremberg, Borussia are not behaving like champions but like an average team in the Bundesliga."

Dortmund, who host Tottenham Hotspur in their Champions League last 16 second leg on Tuesday hoping to overturn a 3-0 deficit, have now won only one of their last seven games in all competitions.

Later Saturday they could see champions Bayern Munich, who visit third-placed Borussia Moenchengladbach, draw level with them on points.

dpa