Bild reports that Nico Schlotterbeck could miss the rest of the season after suffering an injury setback against Eintracht Frankfurt.
However, the centre-back only lasted 25 minutes on the pitch before being replaced by Niklas Süle.
Initial reactions from the BVB camp were positive, but it has now emerged that the injury is more serious than first thought.
According to Bild, Schlotterbeck has suffered a recurrence of the torn muscle fiber injury he suffered in early April.
The final MRI results are still pending, but if they are as bad as feared, Schlotterbeck will most likely be out for the season, according to the report.
At the very least, he will miss Dortmund's game against Bochum on Friday night.