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.
ranked 129 before the event started,
on her way to the third round.
Meanwhile, Rafael Nadal beat Radek Stepanek 6-2 6-2 in the third round.
He will now face Kei Nishikori.
The most pleasing aspect of Watson's defeat, from a British point of view, was how disappointed she was afterwards. No player likes to lose 6-0 6-2, but the scoreline could and probably should have been a little closer and yet Watson knew she did not play to her potential. She told the media afterwards that she had hit more than 40 unforced errors, and shook her head as she said it. Watson expected more of herself, and that bodes well for future improvement.
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
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
who needed three sets to beat Ukraine's Alexander Dolgopolov 6-4 5-7 6-2, and
who overcame German Philipp Kohlschreiber 6-4 7-6 (7-2).
In the women's singles,
came back from a set down to defeat Canadian
4-6 6-4 7-6 (7-5).
defeated Simona Halep in straight sets 6-4 7-6 (8-6) and
defeated Daniela Hantuchova 6-2 7-6 (7-2) to book her place in the fourth round.