VfB Stuttgart's Germany striker Cacau is expected to be out for at least the next three months after tearing both his medial and cruciate knee ligaments in training.
The 31-year-old Brazil-born forward injured his left knee while colliding with Stuttgart defender Antonio Ruediger on Wednesday and a is wearing a special splint to prevent an operation would have kept him out for longer.
"This is obviously very bitter for us and I'm really sorry for Cacau," said Stuttgart's director of sport Fredi Bobic.
"We will support him with everything we can do.
"We're thinking positively and we are hoping that he won't need an operation."
Having made the last of his 23 appearances for Germany in their 5-3 friendly defeat to Switzerland in May, Cacau has scored just once in ten games for Stuttgart this season, with six of those coming from the bench.
He was not included in Joachim Loew's Germany squad for Euro 2012.
Bosnia striker Vedad Ibisevic has scored three goals in his last two Bundesliga games with Stuttgart 15th in the league, just above the relegation zone, ahead of Sunday's league game at Hamburg.