Real Madrid head coach Rafael Benitez has admitted that he is unsure how long Gareth Bale may face on the sidelines after he picked up an injury in the 4-0 win over Shakhtar Donetsk.

Cristiano Ronaldo moved to 80 goals in the Champions League with a hat-trick as Real cruised to victory in their Group A opener.

However, there was concern for the hosts as Benitez was forced to take off Bale in the first half due to a calf problem.

"Injuries are bad news," the Spaniard told reporters. "The team is quite well physically, but we will have to wait one or two days to see the evolution of Bale's injury. Sergio [Ramos] and [Raphael] Varane also have problems but I'm more optimistic about them."

Real have scored 15 goals in their last three matches without conceding.