Williams sisters storm into Miami quarter-finals

Miami (AFP) - Serena and Venus Williams advanced to the quarter-finals of the ATP and WTA Miami Open on Monday, the sisters each cruising to a straight-set triumph.

World number one Serena Williams, seeking a third consecutive Miami crown and record eighth title at the hardcourt event, hammered Russian Svetlana Kuznetsova 6-2, 6-3 while 16th-seeded elder sister Venus defeated fourth seed Caroline Wozniacki 6-3, 7-6 (7/1).

Between them, the Williams sisters have won the Miami singles title 10 times. The only players to win the crown three years in a row are Serena, from 2002-2004, and Steffi Graf, who did it from 1994 to 1996.

Serena, 33, took 73 minutes in beating 2006 Miami champion Kuznetsova, improving her overall Miami record to 70-7.

"I don't think I'm cruising," Serena Williams said. "I have my matches and I'm really focused in my matches because all these players I play are really good.

"When Venus is playing before me I'm always excited to see her results and hopefully (see) a win. But I don't usually watch her match because I'm trying to focus on mine."

Serena could face her sister in the finals. While Venus, who suffers from the chronic medical condition Sjogren's syndrome, has struggled in recent seasons, she has played well in 2015, winning her 46th career title in January at Auckland and making a run to the Australian Open quarter-finals, her deepest at a Grand Slam event since the 2010 US Open semi-finals.

"She's playing really well, she's playing really aggressive," Serena Williams said of her sister. "I have always said what Venus has gone through has really motivated me."

Venus Williams, 34, is playing her home event for the 16th time and owns three titles. The American took the win despite 37 unforced errors in a match riddled with a dozen breaks of serve. Williams has never lost to former number one Wozniacki, now 7-0 against the Dane.

"I'm persistent. I don't give up and I believe in myself no matter what the odds are and what you may experience," Venus Williams said. "I've always seen it as something to overcome and not something that could stop me.

"Having that perspective of glass half full helped me a lot."

Spanish 12th seed Carla Suarez Navarro upset seventh seed Agnieszka Radwanska 5-7, 6-0, 6-4 and will be the next to play Venus Williams.

- Nishikori advances -

In the men's draw, Japan's Kei Nishikori took just over an hour to defeat Serbia's Viktor Troicki 6-2 6-2 to secure a fourth-round berth.

Asia's top player -- who reached the semi-finals in Miami last year -- could not fault his performance.

"I played good tennis today, almost perfect. I'm excited that I'm playing good here. Maybe he was hurting a little bit, but still I was giving him a lot of pressure with my return," Nishikori said.

"It was a great match today. I felt great on the court, so very happy to win."

Nishikori, 25, sent down five aces and 16 winners, breaking 39th-ranked Troicki on five of six chances in a truly dominant performance.

Nishikori, who reached his first Grand Slam final last year at the US Open, beat David Ferrer and Roger Federer on his way to the Miami semi-finals last year only to withdraw prior to a match with Novak Djokovic due to a groin injury.

"It was really sad last year, but I had a great year last year," Nishikori said. "One of the keys was that I got a lot of confidence from the Roger win."

Nishikori cannot repeat that since Federer did not play at Miami this year, but he will next face Belgium's David Goffin, who beat Poland's Jerzy Janowicz 6-4, 6-3.

Alexandr Dolgopolov of Ukraine also reached the fourth rond with a 7-5, 6-4 win over Brazil's Thomaz Bellucci.