World number one Novak Djokovic sped into the Shanghai Masters quarter-finals with a 6-2, 6-3 win over Feliciano Lopez in just 71 minutes as he continued his magical run in China on Thursday.

As Andy Murray and Jo-Wilfriend Tsonga toiled, the unstoppable Serb dominated Spain's Lopez as he brought up his 14th win in a row including a winning streak of 16 straight sets.

Rafael Nadal's recent resurgence, meanwhile, gathered pace when he beat Milos Raonic 6-3, 7-6 (7/6) to set up a quarter-final with Kevin Anderson, who ousted Japanese heartthrob Kei Nishikori 7-6 (12/10), 7-6 (7/3).

A magical backhand lob to break Lopez for 3-1 in the second set underlined the superiority of Djokovic, who claimed his sixth China Open title last week and has lost only five out of 75 matches this year.

"There is no secret. I guess it depends how do you feel on a given day, depends how well your opponent is playing, how well you're playing. It's a combination of things," said the two-time Shanghai champion.  

"You can't just expect to win all the time very comfortably, but I've been doing so for the last week-and-a-half. Obviously it's giving me more confidence. Any time I come back to the court, I feel good and I start off well."

Djokovic's current unbeaten run stretches back to the Cincinnati Masters final in August and with his win in Beijing, he became the first man to top $15 million (13.1 million euros) in prize money in a single year.

He said there was still room for improvement despite putting together what he calls his best season yet, after winning three out of four Grand Slam finals to reach a career total of 10.

"I think it's a combination of... maintaining the high level, the performance, the tennis I have right now, and also working on certain parts of the game that I think can be improved," he said.

"I was brought up that way and thought to always look for some room for improvement. I still believe there are shots in my game that can be better. I think that's one of the things that keeps me going.

"It motivates me to play more."

- Giant-killer felled -

Earlier Andy Murray squeezed past John Isner and Jo-Wilfried Tsonga was also pushed all the way before ending the giant-killing run of Spanish qualifier Albert Ramos-Vinolas.

Murray lost the first set on a tiebreak and he snapped at the umpire as his frustrations rose in the second set, before he finally broke the big-serving Isner and levelled the match at a set each.

The world number two broke again for 4-3 in the decider and he left the American number one on his backside as he fended off break points in his next service game, before going on to take it 6-7 (4/7), 6-4, 6-4.

"Obviously it's tough to maintain your patience and not get a bit frustrated when you do get the chances and, you know, he serves an ace," Murray said.

"There were like 13 break points. I would imagine he served an ace on at least half of those. He served very well when he was behind."

Seventieth-ranked Ramos-Vinolas came through qualifying before he stunned defending champion Roger Federer in the second round -- but Tsonga proved a match too far.

However, the 27-year-old Spaniard gave the mercurial Frenchman a massive scare when he took the first set before going down fighting 6-7 (5/7), 7-5, 6-4 in two hours and 45 minutes.
Source: AFP