- Stanislas Wawrinka equals best result at Miami Masters with win over Edouard Roger-Vasselin
- Swiss is joined in last 16 by world No. 1 Rafael Nadal and John Isner
- Serena Williams and Maria Sharapova both progress to quarterfinals of women's event
- Li Na also progresses to last eight, but Venus Williams loses in three sets
Australian Open champion Stanislas Wawrinka is safely through to the last 16 of the Miami Masters after defeating Edouard Roger-Vasselin of France in straight sets 7-5 6-4.
The world No. 3, who battled past Daniel Gimeno-Traver in the previous round, was again made to work hard by his lower-ranked opponent.
The first set was heading for a tie-break before Wawrinka broke the Frenchman's serve in the 12th game to close out the set in 45 minutes.
The Swiss looked to be running away with the second after opening up a 3-0 lead, but the world No. 43 battled back to 4-4 before Wawrinka broke serve again in the 10th game to take the match.
Wawrinka, who has never gone further than the last 16 in Miami, will now face Alexandr Dolgopolov after the No. 22 seed beat Dusan Lajovic 3-6 6-0 7-6 (7/5).
The Ukrainian, who shocked world No. 1 Rafael Nadal in the third round at Indian Wells this month, edged through in a tiebreak after rain halted play for an hour with the score poised at 5-5 in the final set.
Nadal, a three-time runner-up in Miami, romped into the last 16 on Monday with a 6-1 6-0 thrashing of Uzbekistan's Denis Istomin.
"I played a very complete match. No mistakes, serving with good percentage, and playing a lot of winners. My movements were better than what I did last events," said the Spaniard, who next faces 14th-seeded Italian Fabio Fognini.
Indian Wells semifinalist John Isner also progressed with a straight-sets win, 7-5 6-3 over Spanish 18th seed Nicolas Almagro, and the American will next play world No. 7 Tomas Berdych.
Canada's Milos Raonic is through to the fourth round in Miami for the first time after a dominant 6-1 6-2 win over Spain's Guillermo Garcia-Lopez.
The No. 12 seed will now face Germany's Benjamin Becker who beat Aljaz Bedene from Slovenia 6-3, 7-5.
In the women's draw, Serena Williams is safely through the quarterfinals after defeating compatriot Coco Vandeweghe 6-3 6-1.
The No. 1 seed overpowered her opponent ranked 104 in the world hitting 17 winners and making only 11 unforced errors, but said afterwards that the match was far from one-sided.
"It was a much tougher match than the scoreline showed," Williams said. "CoCo has such an amazing serve, so every time I was returning I was like, 'Hopefully I can touch the ball.' But it was really good for me to win this match today. I love playing here in Miami."
The defending champion will meet fifth seed Angelique Kerber who needed all three sets to get past Russia's Ekaterina Makarova.
The German won the first set comfortably enough before Makarova fought back to take the second. But it was Kerber who prevailed in the final set to take the match 6-4 1-6 6-3.
World No. 2 Li Na thrashed Spanish 15th seed Carla Suarez Navarro 6-0 6-2 to set up a clash with former No. 1 Caroline Wozniacki -- who followed up her win over Sloane Stephens by dispatching Varvara Lepchenko, conceding just one game in both matches.
Maria Sharapova needed three sets to overcome Belgium's Kirsten Flipkens.
The Russian fourth seed lost the opening set, serving five double faults, before battling back strongly to win 3-6 6-4 6-1 and book a place in the quarterfinals.
Sharapova, a runner-up in Miami on five previous occasions, is hoping to break her duck this year.
"Of course you want to be able to hold the winner's trophy, but you also know the matches you've got to get through to get to the final stage," Sharapova said.
"It's not like I didn't have my opportunities in those finals. I just didn't take them. That's why you come back and hope for another chance."
Sharapova will face eighth seed Petra Kvitova after the Czech beat Serbia's Ana Ivanovic 3-6 6-0 6-0.
Dominika Cibulkova ended Venus Williams' hopes of a first Miami title since 2011, with the Australian Open finalist battling to a 6-1 5-7 6-3 over the American 29th seed, the runner-up here in 2010 before problems with an autoimmune disease derailed her career.
The Slovakian will next face Polish third seed Agnieszka Radwanska, who also needed three sets before overcoming Ukrainian 19-year-old Elina Svitolina, 7-6 (7-5) 5-7 6-2.
Cibulkova will break into the top 10 for the first time in her career if she wins Wednesday's quarterfinal clash.