Australia's Daria Saville continued her inspiring comeback following Achilles surgery by racing into the last 16 of the Miami Open.

Meanwhile, Alex de Minaur won his all-Australian duel with Jordan Thompson in straight sets in the second round of the men's draw.

Saville defeated doubles world number one Kateřina Siniaková, who was forced to pull out with injury after a 36-minute pummelling with the scores at 6-0, 1-0.

Siniaková appeared to struggle with an abdomen injury but Saville was merciless, attacking with venom and dropping just nine points in a 23-minute opening set.

It means Saville has now made the fourth round in two successive WTA 1000 events — the biggest women's tournaments outside the majors — in Indian Wells and Miami as her career revival continues.

Less than six weeks ago, Saville was ranked 627 in the world as she trod nervously on the comeback trail after 10 months out of the game following surgery to cure a chronic Achilles problem.

If she can win her eminently winnable last-16 match against qualifying lucky loser Lucia Bronzetti, Saville will be up to at least number 127 when the next rankings come out on April 4.

Naomi Osaka moved into the fourth round without taking to the court.

The former world number one got a walkover victory when Karolína Muchová withdrew citing a need for recovery.

Muchová missed about seven months because of an abdominal injury and had not played since last year's US Open before returning in Miami. 

Osaka beat 13th-seeded Angelique Kerber in the second round and will not have to face another seed until at least the quarterfinals.

Number 22 seed Belinda Bencic made the third round on the top half of the draw, defeating Heather Watson 6-4, 6-1.

Another third-round winner in the women's draw was Australian Open finalist and ninth seed Danielle Collins, who played through neck soreness and downed Vera Zvonareva 6-1, 6-4.

De Minaur impresses

Thompson is among a host of Australian players in the top 100 who are battling to close in on world number 28 de Minaur in the rankings.

Yet the 23-year-old was in no mood to let any of his advantage at the top slip as he took just 68 minutes to beat his fellow Sydneysider 6-2, 6-3.

De Minaur joins another Australian, Nick Kyrgios, in the third round.

After breaking Thompson in just the third game of the match, de Minaur was in command throughout, going on to grab each of the five break points he gained during the fifth match between the two friends.

The only time world number 78 Thompson looked set to make a fight of it was when it was effectively too late, as de Minaur reeled off seven games in a row to race into a 4-0 lead in the second set.

De Minaur's fourth win over Thompson set up a last-32 clash with number three seed Stefanos Tsitsipas, who beat American JJ Wolf 6-4, 6-7 (7-5), 6-1.

Meanwhile, fellow Australian Alexei Popyrin proved no match for Marin Cilic, losing 6-0, 6-3.

In the match of the day, top seed Daniil Medvedev opened his bid to reclaim the number one ranking by defeating Andy Murray 6-4, 6-2.

Medvedev can regain top spot on the rankings by making the Miami semi-finals.

Only five men in the past 18 years have held the number one ranking, which is currently held by Novak Djokovic.

Wires/ABC