Andy Murray received a walkover into the last 16 of the Miami Masters after Milos Raonic pulled out of their third-round clash with an ankle injury.

Canadian Raonic, ranked 26 in the world, injured 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 in the fourth round after he beat Jurgen Melzer.

Frenchman Simon overcame Austrian Melzer 7-6 6-4.

Raonic added: "Yesterday we finished an hour-long session and, just as I was moving back, I rolled my ankle.

"It wasn't getting any better in the doubles and was painful with pretty much every movement this morning.

"It's frustrating, but if I look at the big picture I can see things are going well. Obviously it would be more frustrating if things were going poorly."

World number four Murray beat Alejandro Falla on Friday to reach the third round.

The victory over the Colombian was a return to winning ways for Murray after he lost his opening match at Indian Wells two weeks ago.

On court on Sunday, Serbian Janko Tapsarevic, seeded nine, beat Ukraine's Alexander Dolgopolov 6-4 5-7 6-2 to make the fourth round.

In the women's singles, France's Marion Bartoli defeated Simona Halep in straight sets 6-4 7-6 (8-6) to book a place in the last 16.