While Andy Murray has already started grass court practise at home in the belief he can become Wimbledon champion, world No2 Rafael Nadal continues to reveal his ruthless streak as he bids for a record-equalling fourth successive French Open title.

Nadal crushed Fernando Verdasco 6-1, 6-0, 6-2 to set up a Paris quarter-final with another fellow-Spaniard, Nicolas Almagro, the man who defeated Murray in the third round.

And while Nadal believes that Almagro is "one of the the four players who can win this title" he is aiming to celebrate his birthday tomorrow by sending his opponent packing.

Nadal said: "Here we don't want to have mercy for anybody. We all fight on each point. My next match is against one of the greatest player on clay at the moment.

"It's going to be a very difficult match and I'll try and play my best tennis to win.

"He has a beautiful and very powerful serve, so I will try and impose my rhythm and not let him take the initiative. I will make him run and that, perhaps, is his only weak point.

"If I win, it's going to be a beautiful birthday present. It's going to be a beautiful day and if it's not, well, too bad."

Nadal has shown signs of being vulnerable, with blisters a constant problem and now a bout of dizzyness raising questions about the world No2's ability to last the course at Roland Garos.

But he is quick to dismiss those fears. He said: "I felt a bit dizzy, so I took time to eat a banana, a piece of bread, and it helped me feel better to win this first game. Because at the beginning I was a bit dizzy when I served, and then I started feeling better and better."

Murray, meanwhile, is more confident than ever about his chances at Wimbledon, his self-belief boosted by a new assurance on clay and the knowledge he is striking the ball cleanly and volleying well at the net.

He is now determined to spend as much time as possible on the Queen's Club courts in readiness for the most important pre-Wimbledon tournament.

Murray said: "Queen's is actually one of my favourite tournaments on the tour. Outside of the Grand Slams, it's a beautiful tournament. I've enjoyed the time I've played it before and I'll try to do my best. "I would love to win Wimbledon. I want to try to win the tournament but I am not saying it's going to happen. But I believe that if I play my best tennis I can win, because I have won against a lot of the top players.

"Since starting on clay, I have moved from being about 22, 23 in the rankings up to 11, and getting very close to being in the top 10 again. So it's been very successful."

World No3 Novak Djokovic booked his place in the French Open quarter-finals with a 6-4, 6-3, 6-4 win over local favourite Paul-Henri Mathieu and now plays Latvia's Ernests Gulbis, a player who used to beat him regularly when they were learning the sport.

Fellow Serb Jelena Jankovic, who has struggled with injury throughout the tournament, won 6-3, 7-6 against Agnieszka Radwanska and then complained that the balls are too heavy for the clay courts.

The women's third seed believes a lighter ball, given the amount of shots needed to win a point on clay compared to other surfaces, would cut down the number of arm injuries.

She needed treatment during the match and said: "A lot of players here have been suffering with the arm because of the balls. The balls are a little bit heavier. A lot of players have been complaining that they have some pain and stiffness in their arm, which is not usual.

"I wish I was healthier and could enjoy my matches and, hopefully, I will get better. There was a possibility I could have lost that second set because I was just trying to guide the ball with my arm, which was not enough.

"I needed to go for it, even though I had pain. It's like the whole arm is hurting me. It's like a chain, and I don't know what I have to do. I will see the physios and do my best to recover."

Second seed Ana Ivanovic had no problems setting up a quarter-final with Patty Schnyder by blitzing Petra Cetkovska 6-0, 6-0.