The Swiss player reached the last 16 with a 6-3, 6-4 win against Tunisia's Malek Iaziri.

Wawrinka, the top seed, saved all six break points against him and converted two of his four chances during the 70 minute contest.

He will now face Alexander Zverev of Germany for a place in the quarter-finals after he came back from a set down to defeat John Isner of the United States 6-7, 7-6, 7-6 in a thrilling match.

Switzerland's Roger Federer, who won last week's Indian Wells title and the Australian Open in January, continued his stunning form in 2017 with an assured 6-3, 6-4 win over Rio 2016 Olympic silver medallist Juan Martín del Potro of Argentina.

Fourth seed Federer has won two titles in Miami in 2005 and 2006.

He will now compete for a quarter-final berth against Roberto Bautista Agut after the Spaniard came from a set down to eliminate American Sam Querrey 3-6, 6-2, 6-3.

Czech Tomas Berdych stayed on course to potentially meet Federer in the semi-finals by beating Gilles Muller of Luxembourg 6-3, 6-4 while Belgium's David Goffin required three sets to defeat Argentina's Diego Schwartzman 4-6, 6-3, 7-5.

Reigning French Open champion Garbiñe Muguruza of Spain was forced to retire from her match with Denmark's Caroline Wozniacki after dropping the first set.

Sixth seed Muguruza took a medical timeout, moments after losing the first set in a tiebreak, after feeling dizzy and decided against returning to the court.

Following her opponent's withdrawal, Wozniacki has reached her sixth quarter-final in seven events this year.

World number one Angelique Kerber of Germany cruised into the quarter-finals of the women's singles competition.

Kerber, the top seed, cruised past Japanese qualifier Risa Ozaki 6-2, 6-2 while the Czech Republic's second seed Karolína Plíšková beat compatriot Barbora Strýcová 6-1, 6-4.

There was also a victory for former world number five Lucie Šafářová of the Czech Republic after she defeated Slovakia's Dominika Cibulková 7-6, 6-1 to reach the last eight.