Rafael Nadal is not expecting to repeat the all-conquering clay-court season he enjoyed in 2010, when he won four consecutive tournaments on the red dirt.

8264 - Nadal rules out repeat of historic clay sweep

The world No. 1 is chasing a record seventh consecutive title at the Monte Carlo Masters, which begins this week, as he commences his bid for a sixth French Open crown.

"What I did last year, winning Monte-Carlo, Rome, Madrid and Roland Garros, was historic," Nadal said. "I don't think that I can do it this year. It didn't happen in 50 or 60 years. So I guess I can't do the same two times in a row."

Nadal has been left in the shade at the start of the season by Novak Djokovic, who has put together a 24-match winning streak so far in 2011, including wins over Nadal at the Sony Ericsson Open and BNP Paribas Open.

The Serb is absent from the Monte Carlo tournament due to injury, but Nadal expects him to come back strongly as he bids to snatch the top ranking.

"Of course, it's very open," Nadal said. "Roger [Federer] has a chance; Djokovic as well. I have some advantage in the ATP Rankings for now, but you never know how things will turn out. Novak is playing extremely well. He's got a huge potential and he's on a winning streak which gives him a lot of confidence. So we'll see at the end of the year who will be No. 1."