Tennis: Raonic, Nishikori on course for finals repeat

Baby-faced assassins Milos Raonic and Kei Nishikori both roared into the quarter-finals of the Japan Open on Thursday to remain on course for a repeat of last year's final.

Third seed Raonic, beaten by local hero Nishikori in the 2012 final, overpowered Frenchman Jeremy Chardy 6-4, 6-3, as bright sunshine returned to Tokyo Bay and the roof was finally opened on centre court after a wet start to the $1.43 million event.

Fourth seed Nishikori sent Spain's Feliciano Lopez packing with a 7-6, 6-0 victory, extending his winning streak on the Ariake hard-court to 10 in Japan Open and Davis Cup competition with a swashbuckling display.

Never remotely threatened, world number 11 Raonic did not face a single break point and put Chardy out of his misery with his 17th ace after 76 minutes.

"I feel so comfortable on this court I almost don't have to think," said the Canadian, coming off his fifth career title in Bangkok last weekend. He faces lucky loser Lukas Lacko in the last eight.

"Lukas has nothing to lose. He made the draw in a fortunate situation and made the most of it. He's dangerous so I'll have to play very tight and disciplined."

Slovakian Lacko beat qualifier Edouard Roger-Vasselin 7-5, 6-4 to boost his earnings for the week to $32,000 so far since winning the coin toss to replace injured Frenchman Michael Llodra in the main draw.

Nishikori took seven minutes less than Raonic to advance, taking the first set tiebreak 7-4 with an ace down the middle before dishing out the dreaded "bagel" to Lopez in a 21-minute second set.

He completed the job with a thundering forehand return.

"I didn't feel happy at all about winning a second-round match," said world number 13 Nishikori, who became the host country's first Japan Open winner last year.

"Probably because I'm the defending champion -- I know there's a long way to go.

"It's my home court," added the 23-year-old, steadily rediscovering his form after a nightmare hard-court season which culminated in a shock first-round exit from the US Open.

"I went through some of the biggest mental trauma of my career this summer but I've sorted my head out and I'm finding my rhythm again."

Nishikori burst onto the scene as an 18-year-old by winning in Delray Beach as a 244th-ranked qualifier in 2008, becoming the first Japanese man to win an ATP title since Shuzo Matsuoka in 1992.

He plays Spain's Nicolas Almagro in the last eight after the sixth seed thrashed Argentina's Horacio Zeballos 6-4, 6-2.

Top seed Juan Martin del Potro safely reached the quarter-finals on Wednesday, before former Tokyo champion Jo-Wilfried Tsonga suffered a shock second-round defeat.

Wimbledon champion Andy Murray withdrew to undergo minor back surgery set to keep the Scot out for the rest of the year.

The Japan Open has boasted a glittering list of champions since Ken Rosewall lifted the trophy in 1973 when it became an official tour event. Stefan Edberg holds the record with four wins, including three in a row from 1989-1991.

John McEnroe, Ivan Lendl and Pete Sampras have all won the title, while Roger Federer, Rafa Nadal and Murray have triumphed in recent years.