Real Madrid boss Zinedine Zidane has admitted that he is currently 'unsure' whether Karim Benzema will be fit to face Manchester City in the semi-finals of the Champions League on Tuesday night.

Benzema was forced off in the first period of Real Madrid's 3-2 win over Rayo Vallecano on Saturday with a knee problem, and it had been claimed that the Frenchman would struggle to make the semi-final first leg against Man City next week.

Zidane has refused to officially rule the striker out of contention, but has placed some doubt over his involvement in the European tie.

"We'll evaluate [Benzema], but he didn't take a blow. I thought he did, but for now we'll go back to Valdebebas and see what he has. I hope it's nothing and that he can play on Tuesday, but we don't know yet," Zidane told reporters.

Real Madrid trailed 2-0 inside 14 minutes against Rayo on Saturday, but a header from Lucas Vasquez and brace from Gareth Bale saw Los Blancos record an eighth straight La Liga win and keep themselves in the title hunt.