Nadal, the world No. 1, dropped serve once before claiming a 6-3, 6-1 win over Santiago Giraldo. Nadal had five service breaks and won more points (29-25) off Giraldo's serve than Giraldo managed.
His quarterfinals opponent will be No. 7-seeded Gael Monfils, who topped ninth-seeded Richard Gasquet 6-4, 7-6 (9-7).
Fourth-seeded David Ferrer also advanced in straight sets, knocking off Victor Hanescu 6-3, 6-2, and earned a match Friday against sixth-seeded Jurgen Melzer. Melzer was a 6-7 (2-7), 6-3, 6-2 winner over Albert Montanes. Melzer fought off 13-of-15 break-point situations in the match.
No. 8-seeded Nicolas Almagro handled Nikolay Davydenko while Juan Carlos Ferrero defeated Simone Vagnozzi 7-6 (7-3), 4-6, 6-4. Almagro and Ferrero are paired against each other in the quarterfinals.
The other quarterfinals, which is on the same side of the bracket as Nadal-Monfils, has Feliciano Lopez going against Ivan Dodig. Lopez advanced over Kei Nishikori 6-4, 7-6 (7-5) and Dodig capped Thursday's play with a 7-6 (7-0), 4-6, 6-3 win over 15th-seeded Milos Raonic.
Swim Week Miami Beach 2014 [PHOTOS]