Defending champion Novak Djokovic and world number twos Rafael Nadal and Maria Sharapova have all advanced at the Miami Masters.
Serbian star Djokovic, winner of the past three grand slam singles crowns, reached the quarter-finals with a 7-5, 6-3 victory over French 17th seed Richard Gasquet.
Djokovic will next face the winner of a later match between Spanish fifth seed David Ferrer and Argentina's 11th seed Juan Martin Del Potro.
Nadal, a three-time Miami runner-up who has never lifted the trophy, ousted Japanese 16th seed Kei Nishikori 6-4, 6-4.
British fourth seed Andy Murray ousted French 13th seed Gilles Simon 6-3, 6-4.
The Scotsman, who could face Nadal in the semi-finals, booked a last-eight date against Serbian ninth seed Janko Tipsarevic, who defeated Bulgaria's Grigor Dimitrov 7-6 (7-3), 6-2.
US eighth seed Mardy Fish outlasted Spanish 12th seed Nicolas Almagro 6-3, 6-7 (2-7), 6-3 in other fourth-round matches.
Next for Fish will be Argentina's Juan Monaco, who stopped Andy Roddick - after his memorable win over Roger Federer- with a 7-5, 6-0 victory.
Nadal fired eight aces and won 65 per cent of first-serve points while saving six of the eight break points he faced to advance in two hours and 11 minutes, improving to 16-3 on the season.
"The beginning was very tough," Nadal said.
"I started playing more aggressively. At the end of the first set, I felt that I started to win my serves easier than him. I believe that I had more the control of the game.
"In the second set I started well, 3-0. Just 5-3, I didn't play my best game there and he broke me. Happy to have the break back later and finally win the match."
The Spaniard will face French sixth seed Jo-Wilfried Tsonga in the quarter-finals, after he defeated Florian Meyer of Germany 6-3, 6-2.
On the women's side, second seed Sharapova advanced to the semi-finals with a 6-3, 6-0 victory over Chinese eighth seed Li Na, the Russian beauty snapping a four-match losing streak to the Asian star.
"I came into this match losing to her the last few times," Sharapova said.
"I really wanted to change that."
The match began with five consecutive service breaks but Sharapova found her form at 4-3, winning the last eight games of the match and 12 points in a row in one stretch to move on after 68 minutes.
"I was really consistent in conditions where it was a little gusty and blowing around and I faced a tough opponent too," Sharapova said.
"I did a good job of maintaining my consistency throughout the whole match."
Sharapova will next face Caroline Wozniacki after the fourth seed enjoyed her first ever victory over Serena Williams, winning 6-4, 6-4.
"I knew I had to close it out, she wasn't going to give it me, she was determined," said the Dane, who played intelligent and patient tennis, and made the most of Williams's 36 unforced errors.
"I knew if I didn't take care of my serves it would be difficult."
AFP/ReutersTags: tennis, sport, united-states First posted March 28, 2012 08:07:48