Rangers winger Chris Burke has been put on a special course of vitamins after suffering a mystery virus that has ruled him out against CSKA Moscow.
Chris Burke is unlikely to play against Celtic on Sunday
The 19-year-old has not played since collapsing at Pittodrie on the opening day of the season.
Rangers manager Alex McLeish told his club's website: "Burkey has lost something like four kilos in weight and therefore is short of strength."
Burke will miss the Champions League tie and is doubtful to face Celtic.
"He has been given a special course of vitamins and iron to improve the minerals in his body, which will help him get his strength back," said McLeish.
"The virus has hit him hard and we have to be careful with him."