PARIS - Decoding Rafael Nadal's self-evaluations can be a tricky proposition.

Listen, for example, to the way the top-seeded Nadal spoke about his game and his mind-set after handling 37th-ranked Ivan Ljubicic, 7-5, 6-3, 6-3, yesterday to reach the quarterfinals at the French Open, improve his record there to 42-1 and get closer to tying Bjorn Borg's record of six championships in Paris.

Nadal chastised himself for being "too anxious." He said he needs to "hit the ball with a little bit more conviction." Looking at the big picture, Nadal insisted: "The thing is, you have to be a realist, and today, I'm not playing well enough to win this tournament."

Maybe he's playing possum. Maybe he's being sincere. Or maybe - as explained by Toni Nadal, Rafael's uncle and coach - this is just the way his nephew is.

"All his life, Rafael never had big, big confidence," Toni said. "He's not a guy who thinks, 'Oh, I am so good.' Never. He tries to improve, he tries to play better, every day."

Toni's nephew has done precisely that at Roland Garros. Since falling behind two sets to one against John Isner in the first round last week, he's won 11 consecutive sets. He made half as many unforced errors as 2006 French Open semifinalist Ljubicic, 48-24. He accumulated 20 break points, converting six.

After trailing 4-5, 30-all - "I felt like he felt the pressure," said Ljubicic - Nadal steeled himself and won 30 of the next 32 points on his serve.

"For moments, I am playing well. But for moments, I am still having [a few] mistakes in a row," Nadal said. "That's what cannot happen in the next round."

That's because he'll face No. 5 Robin Soderling, the only man to defeat Nadal at the French Open - in the fourth round in 2009. It's also a rematch of last year's final, which Nadal won in straight sets.

While Nadal and Soderling both advanced with relative ease, 34th-ranked Juan Ignacio Chela put in a lot of work before edging Alejandro Falla, 4-6, 6-2, 1-6, 7-6 (5), 6-2, to return to the Roland Garros quarterfinals for the first time since 2004.

Chela will play No. 4 Andy Murray or No. 15 Viktor Troicki, whose match was suspended because of darkness tied at two sets each.

"I wouldn't have believed it," the 31-year-old Chela said, "if you had told me, 7 years later, I would still be here."

Maria Sharapova went 2 years without getting to the quarterfinals at a Grand Slam tournament, but she made it back by erasing deficits in both sets and beating 12th-seeded Agnieszka Radwanska, 7-6 (4), 7-5. The three-time major champion fell behind 4-1 in the first set, then 5-3 in the second, where she had to fend off five set points.

Sharapova finished with far more winners, 47-13, and unforced errors, 44-12. Her quarterfinal opponent will be No. 15 Andrea Petkovic, who defeated No. 25 Maria Kirilenko 6-2, 2-6, 6-4.