Borussia Dortmund centre-back Neven Subotic faces at least six months out of football after tearing both the cruciate and medial ligaments in his right knee.
"Unfortunately, I haven't got good news to report on my injury, it's a torn ligament in two places," Serbia international Subotic wrote on his Facebook page. "Do not worry, I'll come back stronger."
The 24-year-old suffered the injury just before half-time in yesterday's 2-1 defeat at Wolfsburg, their second defeat of the week after losing 1-0 at home to Arsenal in the UEFA Champions League.
The club has said he will be out for at least six months. "That's terrible news," admitted Dortmund coach Jurgen Klopp.
The timing is bad as second-placed Dortmund host European champions Bayern Munich in the Bundesliga in a fortnight in a repeat of last season's Champions League final with the Bavarians four points clear at the top.
Four days later, Dortmund host Napoli in a crucial match in the Champions League where they are third in Group F following their Arsenal defeat last Wednesday.
Dortmund have only just welcomed back Subotic's centre-back partner, Germany's Mats Hummels, from a back injury, but Borussia can rely on Greece defender Sokratis Papastathopoulos as cover.