Seventh seeded Dimitrov proved in fine form against the Rio 2016 Olympic silver medallist from Argentina as he claimed the first set of the match 6-3.

Del Porto produced a strong challenge in the second set, but was ultimately unable to force a decider in the tie.

A key break of serve allowed Dimitrov to secure a 6-3, 7-5 victory over his opponent.

Dimitrov will now face the challenge of Yūichi Sugita after the Japanese player battled from a set down to claim a 6-7, 6-3, 6-3 win over Russia’s Karen Khachanov.

Tournament third seed Dominic Thiem also progressed to the quarter-finals, with the Austrian seeing off the challenge of France’s Adrian Mannarino.

Thiem won both sets on tie-breaks to secure a 7-6, 7-6 victory.

He will meet David Ferrer in the last eight, with the Spaniard having won 6-4, 6-4 against his compatriot Pablo Carreno Busta.

There will be an all-American quarter-final, following John Isner’s 7-6, 7-5 win over his countryman Frances Tiafoe.

Isner will face Jamie Donaldson following the American wildcard's win against Nikoloz Basilashvili of Georgia 6-4, 7-6.

In the women’s draw, Romania’s Simona Halep claimed a 6-4, 6-3 win over Latvia’s Anastasija Sevastova.

The second seed will be rewarded with a quarter-final tie against Britain’s Johanna Konta, who was a 6-3, 6-4 winner against Dominika Cibulková of Slovakia.

Wimbledon champion Garbiñe Muguruza also earned a place in the last eight as the Spaniard beat the United States’ Madison Keys 6-4, 3-6, 7-6.

Muguruza will now face Svetlana Kuznetsova, with the Russian having cruised past Spain’s Carla Suárez Navarro by a 6-2, 6-4 scoreline.