Real Madrid are waiting to see whether Michael Essien will miss the rest of the year due to an allergic reaction to medicine.
The Ghana midfielder hasn't played since the victory over Levante on November 11 and Real had been keeping quiet as to why the 29-year-old wasn't available.
Real have now shed some light on the matter by revealing the man on loan from Chelsea has had a bad reaction after being given some medicine by the club's doctor.
"He has had an allergic reaction to some medicine," Real assistant Aitor Karanka said.
Reports in Spain now suggest Essien could be out until after the winter break due to the issue, a blow to Jose Mourinho's plans, the "Special One" having used the former Lyon ace in a number of positions this season.
Real have also revealed they haven't put a timescale on when Marcelo and Gonzalo Higuain will return as they continue their recovery from a broken foot and thigh injury respectively.