SHANGHAI -- Weary in body and mind, Rafael Nadal knows there are days when his game simply fails to rise to the moment.
Nadal, winner of three Grand Slam tournament titles this year, lost to Austria's Jurgen Melzer 6-1, 3-6, 6-3 Thursday in the third round of the Shanghai Masters. It was the first time this year the top-ranked Spaniard failed to reach the quarterfinals.
"This isn't a surprise for me. I didn't play well," Nadal said. "I felt slow on court and I made more mistakes than usual. In general, I am a little bit more tired than usual, physically and mentally.
"You can't expect to win every week. All the good work is done for me for the year."
Nadal had not dropped a set to Melzer in three previous meetings and recently beat him in this year's French Open semifinals en route to the title.
Nadal won the U.S. Open in September to become the seventh man in history to win all four Grand Slam tournaments. He was bidding for his eighth title of the season. He won the Japan Open title on Sunday before traveling to Shanghai and said his schedule contributed to the loss.
Melzer, seeded 13th, played aggressively from the start, hitting booming forehand winners. He attacked Nadal's second serve to break twice and capture the opening set in 40 minutes.
"I felt he was uncomfortable after a few games," Melzer said. "When the ball was in play, he sometimes missed and his backhand was just dying in the net. I felt if I kept playing like that and not give him too much rhythm, I'd have my chance."
Nadal rallied in the second set, getting his first -- and only -- break of the match with a running backhand down the line that the Austrian dumped into the net.
The two players held serve in the deciding set until the fifth game when Nadal shanked a forehand long and hit another one wide to give Melzer his third break of the match. The Spaniard saved three match points on his serve, but Melzer easily put the match away on his next serve.
Federer, playing his first tournament since the U.S. Open in September, had to work to beat Italy's Andreas Seppi 6-3, 6-4 to set up a quarterfinal against Robin Soderling. Federer, ranked No. 3, has a 13-1 record against the Swede, who defeated 11th-seeded David Ferrer 7-5, 6-4.
"Even though I have a great record against him, I have a lot of respect for him and am excited about the match," Federer said. "Definitely going to bring the heat on his serve and try to hit hard forehand or backhand."
Murray beat qualifier Jeremy Chardy of France 6-3, 6-4 to reach his ninth quarterfinal this year, assuring his spot in the World Tour Finals in London.
"I served well under pressure," Murray said. "That was really, really important to get a good start in the match because he's very, very streaky."
The Scot has benefited from a relatively easy draw, receiving a first-round bye and beating a 465th-ranked Chinese wild card in the second round. In the quarters, he faces Jo-Wilfried Tsonga. The 12th-seeded Frenchman defeated Germany's Florian Mayer 7-5, 6-3.
Djokovic, aiming to win back-to-back titles after capturing the China Open last week, defeated France's Richard Gasquet 6-1, 6-1.
Gasquet looked drained after winning two matches because of a rain-delayed schedule earlier in the week. He dropped serve five times and had only six winners to 25 for the second-ranked Serb.
"I don't know how [Gasquet] felt and I didn't care," Djokovic said. "I did really well from the start. I put pressure on him and I was aggressive. I didn't give him a chance to come back into the match."
Djokovic will play Spain's Guillermo Garcia-Lopez, who upset Wimbledon finalist and seventh-seeded Czech Tomas Berdych 7-6 (4), 6-3. Garcia-Lopez advanced Wednesday when Andy Roddick quit with a groin injury while leading 6-3, 2-3.