South Korea striker Ji Dong-won netted twice against his former club Borussia Dortmund as the league leaders suffered a shock 2-1 defeat at Augsburg on Friday to stumble again in the Bundesliga title race.
Defending champions Bayern Munich, who are second, will draw level with Dortmund on 54 points if they win at third-placed Borussia Moenchengladbach on Saturday.
The result is a blow for Dortmund as they try to overturn a 3-0 defeat on Tuesday when they host Tottenham Hotspur in the return leg of their Champions League last 16 tie.
Dortmund now have just one win in their last seven matches in all competitions. They have also dropped nine points in their last five league games.
Both Augsburg goals were a result of mistakes by inexperienced Dortmund defenders Dan-Axel Zagadou, 19, and Achraf Hakimi, 20.
“We practically scored their goals ourselves with two individual mistakes,” said Dortmund captain Marco Reus, back after four weeks out with injury.
“We have to stop that. We can’t give away possession so easily, we had enough goal chances to win the game.
“The difference between us and Bayern is that they are in an upward curve and they do not make individual mistakes.”
Having also scored against Bayern a fortnight ago, Ji gave Augsburg the first-half lead, then hit a superb second to chip inside the post home 22 minutes from time.
Paco Alcacer scored Dortmund’s consolation goal nine minutes from time, but victory left Augsburg now five points clear of the relegation battle in 15th place.
This was only Dortmund’s second league defeat this season, but is another significant set-back after being held to a goalless draw at bottom side Nuremberg ten days ago.
“We had to win this match, they (Augsburg) did not create any chances, yet scored two goals – it’s a totally preventable defeat,” said head coach Lucien Favre.
“We had opportunities, we did not put them in and it was big mistakes which gave the ball to the opponent.”
Once again, Dortmund struggled against relegation-threatened opposition as Augsburg gave the perfect response after three straight defeats and last weekend’s 5-1 thrashing by Freiburg.
Augsburg were forced into an early substitution when defender Konstantinos Stafylidis limped off injured after just 17 minutes.
Just as they did a fortnight ago, when mighty Bayern Munich had to twice come from behind to win 3-2 at the WWK Arena, Augsburg took a surprise early lead.
When Andre Hahn fired in a cross, Zagadou slipped and despite the best efforts of three Dortmund defenders, Ji curled home his shot for the opening goal on 24 minutes.
At the other end, defensive midfielder Thomas Delaney shot over the bar and centre-back Manuel Akanji headed wide.
Then Dortmund midfielder Jacob Bruun Larson fired direct at Augsburg goalkeeper Gregor Kobel at point-blank range as the hosts went into the break 1-0 up.
Heavy rain blighted the second-half, but Ji showed lightning reactions for his second goal.
When Hakimi put in a lazy pass, Ji pounced and sprinted clear before chipping the ball inside the far post to delight the home crowd.
The 27-year-old has now scored four goals in seven games against his old Dortmund.
With Reus off, his replacement Alcacer gave Dortmund hope on 81 minutes when he tapped home Mario Goetze’s final pass, but it was too little, too late.
