World number two Rafael Nadal has admitted to being 'a little bit scared' about his perennial knee problem ahead of the Monte Carlo Masters.

Nadal had not trained in two weeks until four days ago because of the issue and the Spaniard was forced to withdraw from last month's Miami Masters semi-final against Andy Murray.

"I couldn't move my knee. I have to try to be patient," said Nadal.

When asked if he found it easy to adapt to playing on clay again, he said: "I don't feel comfortable even today. I need time. I need to spend hours on court, play matches and I need practice.

"I had to stop after Miami for a long time. I started to practise four days ago, so it's not enough."

Nadal hasn't won a tournament for 10 months but has been victorious in every Monte Carlo Masters since 2005, claiming seven consecutive titles.