The Frenchman is yet to return to training after picking up a sprained ankle against Leganes and is now reportedly also suffering from tonsillitis.
According to AS, Dembele was due to return to training on Monday but has been given antibiotics and told to rest after being diagnosed with tonsillitis.
The report reckons recovery usually takes “three to four days” which would rule Dembele out of the match with Real Madrid.
Mundo Deportivo have a similar story, although they report that Dembele has a fever and could be suffering from the flu.
Dembele is not the only doubt for the match. Lionel Messi picked up a slight knock against Valencia and is set to be assessed to see if he’s fit enough to feature.