Top-seeded Novak Djokovic overcame a slow start on Sunday before pulling away to defeat Portugal's Joao Sousa 6-4, 6-1 in the third round of the Miami Open at Key Biscayne, Fla.
Djokovic, from Serbia, was tied at 4-4 in the first set before he began pulling away. He lost just 11 points over the final eight games.
"The first set was very close," Djokovic said. "It could have gone either way. I played well in the right moments."
Djokovic is in pursuit of his sixth win at the event, which would tie Andre Agassi's men's record.
The match took 2 hours, 42 minutes and Johnson was unable to score a break point, coming up empty on all 10 opportunities.
Argentina's Horacio Zeballos continues to take advantage of his good fortune and posted a 1-6, 6-4, 7-6 (4) victory over Spain's Fernando Verdasco. Zeballos lost in qualifying but was added to the main draw when Roger Federer withdrew due to a stomach virus.
Austria's Dominic Thiem beat qualifier Yoshihito Nishioka of Japan 6-2, 6-2, Belguim's David Goffin was a 6-1, 6-1 winner over Serbia's Viktor Troicki and Richard Gasquet was a 6-3, 6-0 victor over Benoit Paire in a battle of Frenchmen.
On the women's side, Victoria Azarenka sailed through two sets and defeated Poland qualifier Magda Linette 6-3, 6-0.
Azarenka, of Belarus, advances to the fourth round and is trying to follow up last week's championship at Indian Wells with another one in Miami.
Second-seeded Angelique Kerber of Germany started off sluggishly before rallying for a 1-6, 6-2, 3-0 over Kiki Bertens of the Netherland, a qualifier who retired in the third set.
Fourth-seeded Garbine Muguruza of Spain had an easy time beating wild-card entrant Nicole Gibbs of the United States 6-1, 6-0.
American Madison Keys defeated ninth-seeded Roberta Vinci of Italy 6-4, 6-4; Great Britain's Johanna Konta defeated Russia's Elena Vesnina 4-6, 6-1, 7-6 (3); Romania's Irina-Camelia Begu ousted Czechoslovakia's Kristyna Pliskova 7-5, 4-6, 6-4; Romanian's Monica Niculescu swept American Coco Vandeweghe 6-4, 6-1, and Hungary's Timea Babos was a 7-5, 6-0 winner over Japan's Naomi Osaka.