Heather Watson's winning run in the Miami Masters ended with an emphatic 6-0 6-2 defeat to world number one Victoria Azarenka.
Azarenka, who recorded her 25th consecutive victory, dropped serve in the second set but recovered to book her place in the last 16.
Meanwhile, Rafael Nadal beat Radek Stepanek 6-2 6-2 in the third round.
He will now face Kei Nishikori.
Andy Murray received a walkover after Milos Raonic pulled out of their third round clash with an ankle injury.
Canadian Raonic, ranked 26 in the world, hurt his ankle in practice and was forced to withdraw three games into a doubles match on Saturday.
"Playing against an opponent the calibre of Andy at only 40% fitness didn't make much sense," said Raonic.
Murray meets Gilles Simon, who beat Jurgen Melzer 7-6 6-4, in the fourth round.
World number four Murray beat Alejandro Falla on Friday to reach the third round.
Victory over the Colombian was a return to winning ways for Murray after he lost his opening match at Indian Wells two weeks ago.
Elsewhere in the men's draw on Sunday, there was an upset when world number seven Tomas Berdych of the Czech Republic crashed out 6-3 2-6 6-4 to Grigor Dimitrov.
It was the Bulgarian's first win over a top 10-ranked player.
Also into the fourth round are ninth seed Janko Tipsarevic, who needed three sets to beat Ukraine's Alexander Dolgopolov 6-4 5-7 6-2, and Jo-Wilfried Tsonga, who overcame German Philipp Kohlschreiber 6-4 7-6 (7-2).
In the women's singles, Venus Williams came back from a set down to defeat Canadian Aleksandra Wozniak 4-6 6-4 7-6 (7-5).
France's Marion Bartoli defeated Simona Halep in straight sets 6-4 7-6 (8-6) and Ana Ivanovic defeated Daniela Hantuchova 6-2 7-6 (7-2) to book her place in the fourth round.