I'm not playing well enough to win title, says Nadal

World number one Rafael Nadal insists he isn't playing well enough to win a sixth French Open title as a Wednesday quarter-final looms with Roland Garros bogeyman Robin Soderling.

The 24-year-old Spaniard, who has cut a world-weary figure both on and off the court, complaining he sometimes feels as if he's been on tour for "100 years", is a champion under pressure.

World number two Novak Djokovic, on a staggering 43-match unbeaten run, is tipped to take the Spaniard's Paris title, as well as the number one ranking, after picking up the Australian Open and six other titles this year.

Two of those were Nadal's Madrid and Rome Masters claycourt crowns in the run-up to Roland Garros.

"I am not playing enough well to win this tournament. That's the truth," said Nadal, who needs one more French Open to equal Bjorn Borg's record of six.

"You have to be realistic. But I have won here five times already. I don't have an obligation to win six."

Nadal's mood would not have been improved by seeing Djokovic's scheduled quarter-final opponent, Italy's unseeded Fabio Fognini, pull out with a torn left thigh muscle.

While the Serb rests until Friday's semi-finals, Nadal returns to court on Wednesday to tackle Swedish fifth seed Soderling for the third year in succession in Paris.

It was Soderling who famously sent Nadal crashing to his first and only defeat at the tournament in the fourth round in 2009 before the Spaniard gained revenge in the 2010 final.

Nadal's record at Roland Garros now stands at 42-1 but Soderling remains one of only two men to have defeated both Nadal and Roger Federer at Grand Slams.

Unlike Nadal, who needed five sets to defeat giant American John Isner in the first round, Soderling has cruised into the last eight virtually unnoticed.

The Swede had also made the last two finals, losing to Federer in the 2009 title match.

"It will be a tough match. He's one of the best players. He's played two finals here at Roland Garros, so he knows what this means," said Nadal.

Soderling, who was once described by Nadal as one of the most unpopular players in the locker room after a bad-tempered clash at Wimbledon in 2007, believes he has the weapons to surprise his old rival.

That's despite Nadal holding a 5-2 career record over the Swede.

"When I won against Rafa in the fourth round in 2009, I proved to myself that I could do well in Grand Slams, and it helped me a lot," he said.

Wednesday's other quarter-final will feature unseeded 31-year-old Argentine Juan Ignacio Chela, who is in the last eight for the first time since 2004, when he was defeated by Britain's Tim Henman.

Chela had to wait until Tuesday to discover his opponent after British fourth seed Andy Murray and Victor Troicki, the Serbian 15th seed, were locked at two sets each when darkness halted their last 16 tie on Monday.

Chela revealed that he has been granted a new nickname of 'Torino' after the classic Ford car that last rolled off the production lines in 1976.

It stems from an incident in a recent Davis Cup tie when he was judged too old to play a gruelling five-setter.

"Against a Torino it's very difficult because this Torino is like a brand new car," his coach told the doubters.

After his five-set win over Alejandro Falla in the last 16, Chela even signed his autographs as 'Torino'.

Chela trails Murray 6-1 in career meetings and is 1-0 down against Troicki.

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