Borussia Dortmund conceded two goals in three minutes to slump to a 2-1 loss at Freiburg on Saturday and drop 16 points behind leaders Bayern Munich while putting their hopes of a Champions League spot next season at risk.
Dortmund, who needed extra time to beat second tier club Paderborn 3-2 in the German Cup on Tuesday, have long given up on the title but their third loss in the last four league games meant they remained in sixth place.
"It is frustrating to be here and be saying the same things but we just have to keep working hard and stay positive," said Dortmund coach Edin Terzic.
"I am angry because we made mistakes that should not be happening. There is no one button you can press and change things. We need to be prepared to go the extra mile."
Freiburg, who won their first game in 11 years against Dortmund to climb to eighth place on 30 points, stunned the visitors with two goals in three minutes after the break with Jeong Woo-yeong firing in from 20 metres in the 49th minute.
Jonathan Schmid then also tried a shot with keeper Marwin Hitz getting his hands on it but sending it onto the post and into the back of the net in the 52nd as Freiburg celebrated a memorable win in their 700th Bundesliga match.
Emre Can had hit the crossbar in the first half for Dortmund but they were dazed following the double strike after the break and took too long to react.
The introduction of teenager Youssoufa Moukoko gave them some inspiration and he hit the post once more.
The 16-year-old then cut the deficit in the 77th firing in from a tight angle for his second league goal after a good run from Erling Haaland.
But the visitors could do nothing to avoid their fourth loss in the last five away matches.
Dortmund are on 32 points, three off Bayer Leverkusen, winners 5-2 over VfB Stuttgart, in fourth place that leads to the Champions League.
Borussia Moenchengladbach missed their chance to overtake Dortmund, losing 2-1 at home to struggling Cologne courtesy of a brace from Elvis Rexhbecaj.
Gladbach remain in seventh, also on 32 points.
(Reporting by Karolos Grohmann; Editing by Christian Radnedge)
