Former US Open champions Marin Cilic and Juan Martin del Potro powered into the fourth round of the Miami Open on Sunday with straight-sets victories.

Argentina's fifth-seeded del Potro, chasing his second ATP Masters title in as many weeks, breezed past Japan's Kei Nishikori 6-2, 6-2.

Ranked sixth in the world after vanquishing Swiss great Roger Federer in the final at Indian Wells last weekend, del Potro needed just 73 minutes to book a fourth-round meeting with Filip Krajinovic of Serbia, who beat France's Benoit Paire 6-3, 6-3.

Second-seeded Cilic also reached the fourth round with a 7-5, 7-6 (7/4) victory over Canadian Vasek Pospisil.

Cilic and del Potro are the biggest names left in a field lacking star power thanks to the early exits of Federer and Novak Djokovic and the injury absences of Rafael Nadal and Andy Murray.

Del Potro, the hottest player on the ATP tour right now, is actually in search of a third straight ATP crown after back-to-back victories in Acapulco and Indian Wells.

His win in the California desert was his first in a Masters 1000 event, a welcome milestone after a succession of injury setbacks almost forced him into retirement in 2015.

In other third-round action, South Korean Chung Hyeon posted a convincing 6-1, 6-1 victory over American qualifier Michael Mmoh.

Chung, who has yet to drop a set in Miami, needed just 63 minutes to advance to a meeting with Portugal's Joao Sousa, who rallied for a 1-6, 6-3, 6-4 win over American Jared Donaldson.

Men results 3rd rd

• Juan Martin del Potro (ARG x5) bt Kei Nishikori (JPN x26) 6-2, 6-2
• Filip Krajinovic (SRB x22) bt Benoit Paire (FRA) 6-3, 6-3
• Joao Sousa (POR) bt Jared Donaldson (USA) 1-6, 6-3, 6-4
• Chung Hyeon (KOR x19) bt Michael Mmoh (USA) 6-1, 6-1
• Marin Cilic (CRO x2) bt Vasek Pospisil (CAN) 7-5, 7-6 (7/4)