Isner produced a superb display in a 7-6, 6-3 win as the misery for the seeded players in the men's draw continued at the Crandon Park Tennis Centre.

Cilic follows the likes of world number one Roger Federer and Novak Djokovic in exiting the tournament before the business end.

Hyeon Chung of South Korea, who reached the semi-finals of the Australian Open earlier this year, awaits for Isner in the last eight after he beat Joao Sousa of Portugal 6-4, 6-3.

Argentina's Juan Martin del Potro, who arrived in Miami having won the Indian Wells Masters earlier this month, is also through after he overcame Filip Krajinović of Serbia 6-4, 6-2.

Del Potro will face Milos Raonic in the quarter-finals after the Canadian dispatched Frenchman Jeremy Chardy 6-3, 6-4.

Controversial Australian Nick Kyrgios, who was involved in a row over Twitter with Spain's Fernando Verdasco yesterday, is out as he lost 6-4, 6-4 to fourth seed Alexander Zverev of Germany.

Zverev will play Borna Ćorić of Croatia, a 7-6, 4-6, 6-4 winner over Canadian Denis Shapovalov, in the next round.

In the women's draw, unseeded Belarusian Victoria Azarenka knocked out fifth seed Karolína Plíšková of the Czech Republic 7-5, 6-3 to reach the semi-finals.

Azarenka was joined by US Open champion Sloane Stephens, who beat German 10th seed Angelique Kerber 6-1, 6-2.

The tournament in Miami continues tomorrow.