Lopez, who has struggled for form this season, relied heavily on his serve, dominating on his own delivery and serving 13 aces as he prevailed in just under two hours.

In the last eight he will now face Argentina's Carlos Berlocq, who breezed past Bjorn Phau 6-1 6-0.

Two seeds bowed out in the round of 32 as both Alex Bogomolov Jr and Ivo Karlovic were beaten.

Seventh seed Bogomolov slipped up against teenager Ryan Harrison, losing 4-6 6-3 6-4, while the number eight Karlovic was beaten 7-6 (7/5) 2-6 6-3 by another American, Bobby Reynolds.

There were no such issues for fifth seed Kevin Anderson, who beat Joao Souza in straight sets.