Miami - World number one Novak Djokovic moved closer to a possible fourth Miami Open trophy Monday by defeating Belgium's Steve Darcis 6-0, 7-5 to reach the fourth round.
Defending champion Djokovic, seeking his third March hard-court double of Indian Wells and Miami in the same year, fired five aces and broke Darcis five times.
Djokovic will next play Ukraine's Alexandr Dolgopolov, who ousted Brazil's Thomaz Bellucci 7-5, 6-4.
Australian Open winner Djokoivic wrapped up victory with a break in the final game to earn his 21st victory of the season as he pursues his third title of the year.
Djokovic needed less than half an hour to take the first set but had to come back from a break down in the second, trailing 5-4 before rallying for the triumph.
"The first set went completely my way, but I had a drop of intensity and didn't use opportunities early in the second set, made it close," Djokovic said.
"I managed to come back in the right moment. I elevated the intensity and started playing a little bit of depth on the ball. But I still complicated my life in the second set.
"t the end of the day, it's a win."
Japan's Kei Nishikori took just over an hour to defeat Serbia's Viktor Troicki 6-2 6-2 to secure a fourth-round berth.
Asia's top player - who reached the semi-finals in Miami last year - could not fault his performance.
"I played good tennis today, almost perfect. I'm excited that I'm playing good here. Maybe he was hurting a little bit, but still I was giving him a lot of pressure with my return," Nishikori said.
"It was a great match today. I felt great on the court, so very happy to win."
Nishikori hit five aces and 16 winners, breaking 39th-ranked Troicki on five of six chances.
Nishikori, who reached his first Grand Slam final last year at the US Open, beat David Ferrer and Roger Federer on his way to the Miami semi-finals last year only to withdraw prior to a match with Djokovic due to a groin injury.
Next up for Nishikori will be Belgium's David Goffin, who beat Poland's Jerzy Janowicz 6-4, 6-3.
Canadian fifth seed Milos Raonic overcame a second-set swoon before recovering to defeat Frenchman Jeremy Chardy 6-1, 5-7, 7-6 (7/3) while Spanish sixth seed David Ferrer beat Lukas Rosol 6-4, 7-5.
In women's play, Serena and Venus Williams advanced to the quarter-finals, each cruising to a straight-set triumph.
World number one Serena Williams, seeking a third consecutive Miami crown and record eighth title at the hard-court event, hammered Russian Svetlana Kuznetsova 6-2, 6-3 while 16th-seeded elder sister Venus defeated fourth seed Caroline Wozniacki 6-3, 7-6 (7/1).
Between them, the Williams sisters have won the Miami singles title 10 times. The only players to win the crown three years in a row are Serena, from 2002-2004, and Steffi Graf, who did it from 1994 to 1996.
Serena, 33, took 73 minutes in beating 2006 Miami champion Kuznetsova, improving her overall Miami record to 70-7.
"I don't think I'm cruising," Serena Williams said. "I have my matches and I'm really focused in my matches because all these players I play are really good.
"When Venus is playing before me I'm always excited to see her results and hopefully (see) a win. But I don't usually watch her match because I'm trying to focus on mine."
Serena could face her sister in the finals. While Venus, who suffers from the chronic medical condition Sjogren's syndrome, has struggled in recent seasons, she has played well in 2015, winning her 46th career title in January at Auckland and making a run to the Australian Open quarter-finals, her deepest at a Grand Slam event since the 2010 US Open semi-finals.
"She's playing really well, she's playing really aggressive," Serena Williams said of her sister. "I have always said what Venus has gone through has really motivated me."
Venus Williams, 34, is playing her home event for the 16th time and owns three titles. The American took the win despite 37 unforced errors in a match riddled with a dozen breaks of serve. Williams has never lost to former number one Wozniacki, now 7-0 against the Dane.
"I'm persistent. I don't give up and I believe in myself no matter what the odds are and what you may experience," Venus Williams said. "I've always seen it as something to overcome and not something that could stop me.
"Having that perspective of glass half full helped me a lot."
Spanish 12th seed Carla Suarez Navarro upset seventh seed Agnieszka Radwanska 5-7, 6-0, 6-4 and will play Venus Williams next.
Results on Monday from the sixth day of the ATP and WTA Miami Open (x denotes seeded player):
Carla Suarez Navarro (ESP x12) bt Agnieszka Radwanska (POL x7) 5-7, 6-0, 6-4
Venus Williams (USA x16) bt Caroline Wozniacki (DEN x4) 6-3, 7-6 (7/1)
Serena Williams (USA x1) bt Svetlana Kuznetsova (RUS) 6-2, 6-3
Sabine Lisicki (GER) bt Sara Errani (ITA x11) 6-1, 6-2
Andrea Petkovic (GER x9) bt Ekaterina Makarova (RUS x8) 6-1, 7-5
Karolina Pliskova (CZE x14) bt Daria Gavrilova (RUS) 6-3, 6-2
Sloane Stephens (USA) bt Belinda Bencic (SUI) 6-4, 7-6 (7/5)
Simona Halep (ROM x3) bt Flavia Pennetta (ITA x15) 6-3, 7-5
Kei Nishikori (JPN x4) bt Viktor Troicki (SRB x32) 6-2, 6-2
Alexandr Dolgopolov (UKR) bt Thomaz Bellucci (BRA) 7-5, 6-4
David Goffin (BEL x18) bt Jerzy Janowicz (POL) 6-4, 6-3
Novak Djokovic (SRB x1) bt Steve Darcis (BEL) 6-0, 7-5
David Ferrer (ESP x6) bt Lukas Rosol (CZE x26) 6-4, 7-5
Milos Raonic (CAN x5) bt Jeremy Chardy (FRA x31) 6-1, 5-7, 7-6 (7/3)
Gilles Simon (FRA x12) bt Alejandro Falla (COL) 6-3, 6-4
John Isner (USA x22) bt Grigor Dimitrov (BUL x9) 7-6 (7/2), 6-2