Borussia Dortmund manager Lucien Favre praised Fortuna Dusseldorf after his side fell to a first Bundesliga defeat of the season at Esprit Arena.
BVB were sluggish throughout and fell behind after Dodi Lukebakio raced through on goal to finish beyond Roman Burki before Jean Zimmer thrashed home an absolute scorcher to put the hosts two goals up.
Paco Alcacer came off the bench to pull one back after neat work from Jadon Sancho and Lukasz Piszczek but Dortmund couldn't force an equaliser and Favre admitted Dusseldorf deserved their victory.
He said, as quoted by Dortmund's website: "They countered very well, that was probably their plan. They sat back very deep and we couldn't find the gaps. The second half was better, but then we conceded the second goal. They played well tactically."
Dortmund's chances of a positive result were scuppered by injuries to Manuel Akanji and Abdou Diallo and Favre says he is unsure who he will pick at centre back for Friday's game against Borussia Monchengladbach.
"We can't avoid everything. We need to wait and see who'll be capable of playing at centre back on Friday. Today both Akanji and Diallo went off with injuries. Zagadou is injured as well."
Monchengladbach are currently six points behind Dortmund, who are top of the Bundesliga, while Bayern Munich are nine points behind with a game in hand, a home tie against RB Leipzig on Wednesday.
After Friday's game, Dortmund do not play again until they visit RB Leipzig on January 19.