Miami Open: Top-ranked Novak Djokovic beats Joao Sousa to power into last 16

World number one Novak Djokovic advanced to the fourth round of the ATP and WTA Miami Open on Sunday, defeating Portugal`s 38th-ranked Joao Sousa 6-4, 6-1.

Two-time defending champion Djokovic, trying to match Andre Agassi`s record of six career Miami titles, needed only 78 minutes to win his 12th match in a row at the hardcourt event and 26th in his past 27 Miami starts.

"That first set could have gone either way," Djokovic said. "I managed to hit the right balls at the right moment and make it to the finish."

The 28-year-old Serbian, who won his 11th Grand Slam crown at the Australian Open two months ago, also has crowns at Doha and Indian Wells this year and hopes to complete the Miami-Indian Wells sweep for the third consecutive year.

Djokovic`s next foe will be Austrian 14th seed Dominic Thiem, who dispatched 124th-ranked Japanese qualifier Yoshihito Nishioka 6-2, 6-2 in 64 minutes.

"He has one of the most powerful baseline games in tennis," Djokovic said of Thiem.

"He likes to construct his points so I will try and take away his time. He`s had one of the best years of his life. He`s beaten Nadal on clay. He`s one of the players in the next generation we should all look out for."

Thiem captured his fifth career ATP title last month by beating Australia`s Bernard Tomic in the Acapulco final and downed 14-time Grand Slam winner Rafael Nadal on the way to a Buenos Aires claycourt crown.

"I`m sure he wants to showcase all that he`s got in his arsenal but I will be sure to be ready for him," Djokovic said.

Sousa fell to 0-3 against Djokovic and 1-21 against top-10 foes with his 19th such loss in a row since beating David Ferrer in Kuala Lumpur in 2013.

"He came out with a clear game plan," said Djokovic. "He wanted to take his chances. He did not have much to lose. It can be dangerous. I know the importance of stepping up a few levels and delivering my `A` game."Reigning Australian Open champion Angelique Kerber and last week`s Indian Wells winner Victoria Azarenka, who each upset world number one Serena Williams in the final to win those titles, reached the last 16 on the women`s side.

German second seed Kerber advanced 1-6, 6-2, 3-0 when 108th-ranked Dutch qualifier Kiki Bertens retired due to illness.

"I was not finding a rhythm at the beginning of the match," Kerber said. "I had to stay strong, believe and keep fighting. I hope she gets well soon but I`m glad to be in the next round."

Kerber next faces Hungary`s 49th-ranked Timea Babos, who ousted 18-year-old Japanese 104th-ranked wildcard Naomi Osaka 7-5, 6-0.

Eighth-ranked Azarenka, a 26-year-old from Belrus who won 2009 and 2011 Miami titles, eliminated Polish qualifier Magda Linette 6-3, 6-0.

She next faces last year`s Wimbledon runner-up, Garbine Muguruza. The Spanish fourth seed ripped 74th-ranked US wildcard Nicole Gibbs 6-1, 6-0 in 55 minutes.

Two-time Australian Open champion Azarenka is trying to become only the third woman to take Indian Wells and Miami in the same year after Graf in 1994 and 1996 and Kim Clijsters in 2005.Argentina`s Horacio Zeballos, a lucky loser who replaced Roger Federer in the draw when the 17-time Grand Slam champion withdrew due to illness, advanced to the fourth round by overcoming Spain`s Fernando Verdasco 1-6, 6-4, 7-6 (7/4).

Zeballos, ranked 112th, had not won a match since last July before beating countryman Juan Martin Del Potro in the second round. After winning two in a row for the first time in more than two years, he faces Indian Wells semi-finalist David Goffin for a quarter-final berth.

"Life changed for me a lot here," Zeballos said. "Beating `DelPo` and Verdasco, two better players than me, I greatly improved both the ranking and economically."

The South American is assured $67,590, which will help since his wife is due to give birth to their first child on April 10.

"I am living happy moments," he said.