"There is a 90 per cent chance that he will not be able to play in the game," said Real's chief of medical staff Alfonso del Corral. "But we will be working hard with the remaining 10 percent in the hope that we can get him ready in time."
The Brazilian striker scored the opening goal in Real's 2-1 win over the Italian side in the first leg at the Bernabeu on Tuesday, but was forced to leave the pitch early in the second half after sustaining the injury to his left leg.
Real said that tests revealed that he had suffered a small tear in his calf muscle and was likely to be out of action for between seven and 10 days.
On a more positive note for Real coach Vicente del Bosque, Spanish international striker Raul has made a rapid recovery from his recent appendix operation and is likely to be available to play in the decisive match at the Delle Alpi.