er 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, who was two points from taking the first set there -- 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 of Sweden, 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 Monday, 34th-ranked Juan Ignacio Chela of Argentina put in a lot of work before edging Alejandro Falla of Colombia 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 even at two sets each. "I wouldn't have believed it," the 31-year-old Chela said, "if you had told me, seven years later, I would still be here." In an on-court interview after he eliminated No. 18 Gilles Simon of France 6-2, 6-3, 7-6 (5), Soderling was told that some people -- including, as it happens, Nadal himself -- are saying the five-time champion isn't at his best. That drew a comment of "I hope not," and an accompanying chortle from Soderling. "No, seriously, he's a great player. I think everybody knows what he can do. He won here so many times," continued the Swede, who lost to Roger Federer in the 2009 French Open final. "Every match is different. It doesn't matter how you got to the quarters, as long as you're there." Novak Djokovic might say the same about how he got to the semifinals. The No. 2-seeded Serb's quarterfinal opponent, Fabio Fognini of Italy, pulled out of the tournament Monday because he hurt a left leg muscle during his five-set win a day earlier. That won't count as a victory for Djokovic, so his winning streak stays at 43 matches overall -- he's 41-0 in 2011 -- heading into what could be a semifinal against 16-time Grand Slam champion Federer. Djokovic wrote on Twitter: "Walkover from Fognini. Bad luck for him, hope he recovers fast. Today i get to enjoy Paris in a different way :-)" There's plenty of time for sightseeing: Djokovic is off until Friday's semifinals. Nadal was asked