Francis Amuzu suffered a quadriceps injury against Kortrijk; he had a successful examination on Tuesday, but there was too much liquid in the area of the injury, making it impossible to determine a period of inactivity.
The injury has blocked the winger's chance to link up with the Belgian national team during the international break.
Amuzu was chased persistently by French club Nice during the summer transfer window. Nice offered 10 million euros but Anderlecht rejected it. Amuzu had a personal agreement with Nice but his club were determined to hold him.
According to reports in Belgium the wingers will sign a new contract in the coming days.