Second seed Novak Djokovic continued his imperious form in China with a 6-4, 6-2 thrashing of Rainer Schuettler to reach the Shanghai Masters quarterfinals yesterday.

As the debate about the draining effects of the long men's season continued, Stanislas Wawrinka and Gael Monfils became the sixth and seventh players to retire from the $3.24 million tournament.

Serbian Djokovic, who will move up to No 3 in the world next week, proved in winning the season-ending Masters Cup here last year that he has the legs to outlast his rivals.

The 22-year-old also won the China Open title in Beijing last weekend and his 84-minute victory over qualifier Schuettler was his ninth in a row on Chinese soil.

The 33-year-old German only made it to the third round because compatriot Tommy Haas pulled out injured and he never looked like having the game to worry Djokovic.

Djokovic rode through his customary lapse, a double fault when he was serving for the first set which gifted Schuettler a break, and sealed the win with two aces.

Sixth seed Nikolay Davydenko earlier defused Fernando Gonzalez's serve with his mobility along the baseline to grab a sixth win in six meetings against the Chilean, 6-3, 7-5.

"If he has a second serve, I know I have a 90 percent chance to win the point," said the seemingly indefatigable 28-year-old.

"He has good motivation when he makes first serves and winners from the forehand."

Swede Robin Soderling later upset error-prone French fifth seed Jo-Wilfried Tsonga 6-3, 6-3 in their encounter under the open roof of the Qizhong central arena.

Tsonga, who won his third title of the season last week in Tokyo, was consistent only in missing the lines and Soderling resisted a brief revival to seal victory with three aces and a volley.

Davydenko, Tsonga, Soderling and Gonzalez are all in with a chance of claiming one of three spots still up for grabs at the season-ending World Tour Finals in London next month.

"I know that if I play well, I have a chance but this tournament won't decide who's going to play in London," said Soderling. "There is still a lot of tennis to be played."

Swiss Wawrinka, the beneficiary when Andy Roddick was injured on Tuesday, lost 3-6, 7-6, 4-2 to Czech Radek Stepanek when abdominal pains caused him to withdraw. French 11th seed Monfils was also down, 6-2, 3-0 to Croatian Ivan Ljubicic, when he quit because of a back injury.