Top seeds Roger Federer and Novak Djokovic cruised into the third round of the Shanghai Masters on Wednesday as defending champion Andy Murray progressed without even picking up a racquet.

As the tournament kicked into life with the introduction of the big guns, America's Sam Querrey sent Kei Nishikori tumbling 2-6, 6-1, 6-4 just days after his opponent became the first Japanese player to win the Japan Open.

Swiss world number one Federer, battling to cling on to his top ranking, beat Taiwanese qualifier Lu Yen-hsun 6-3, 7-5 to set up a clash with fellow countryman Stanislas Wawrinka.

Federer's build-up to the Shanghai tournament was clouded by a death threat from a blogger in China but the 17-time Grand Slam champion said he quickly put it out of his mind once he was on court.

"I thought it was a good match for me. Obviously not having been broken is a good thing early on in a tournament. You hope it sets a trend for more to come," he said.

Speaking about the threat, Federer said: "I felt fine, you know. There was maybe one quick thought." But he added: "Once the match started, got under way, I never thought about it again."

Djokovic, who will regain the world number one ranking if he wins the title and Federer loses before the quarter-finals, dismissed Bulgaria's Grigor Dimitrov 6-3, 6-2 in just 54 minutes.

"Very pleased with my serving in Beijing and obviously the first match today," said the second seed, who lost just five of his service points. "So that's something that I've been working on, obviously."

The Serbian will next play Spaniard Feliciano Lopez, who beat German 16th seed Philipp Kohlschreiber 6-3, 6-4.

US Open champion Andy Murray did not even have to take to the court as Germany's Florian Mayer withdrew with a rib injury, giving the Scot a walkover. He has still not played yet as the top eight seeds had a first-round bye.

"I'll practise again. I mean, you never know whether it's a good or a bad thing. I mean, you're obviously prepared to play the match," said third seed Murray, who next faces Alexandr Dolgopolov of the Ukraine.

Japan's Nishikori, suffering from an ankle problem, was brought down to earth with a bump after his title win despite a strong start against Querrey, who won five straight games from 4-1 down in the decider to seal the match.

Nishikori, at a career high of number 15 in the rankings after his weekend win on home soil against Canada's Milos Raonic, had on-court treatment on his right ankle, which he said had been bothering him since last week.

"I tried to play but he had a good serve," he said. "I broke him first in the third set but couldn't finish the match. It's disappointing but I was close to win with this injury. Nothing I can do," he said.

There were second round wins for fourth seed Tomas Berdych of the Czech Republic, fifth-seeded Frenchman Jo-Wilfried Tsonga, sixth seed Janko Tipsarevic of Serbia and 13th seed Wawrinka.

But among the seeds to fall were Raonic and the French pair of Richard Gasquet and Gilles Simon.

As the season enters its final stages there are four places still up for grabs at next month's season-ending World Tour Finals in London. Federer, Djokovic and Murray have all qualified, along with the injured Rafael Nadal.