Nadal lost serve just once in a 6-4, 6-4, 6-2 decision over Lopez. The match was relatively lengthy for Nadal -- 2 hours, 45 minutes -- but Nadal still took 58 percent of the points, including 77 percent on serve.
He also won nearly half (50-of-109) of the points when receiving and finished off five of his 18 break-point chances versus Lopez, who was the No. 18 seed.
Seventh-seeded Tomas Berdych earned a quarterfinal shot at Nadal with a taut 4-6, 7-6 (7-5), 7-6 (7-3), 7-6 (7-2) win against 10th-seeded Nicolas Almagro. Berdych managed just one break in the nearly 4-hour match but survived with the advantage in the tiebreakers.
Roger Federer, seeded third, took out unseeded Australian Bernard Tomic 6-4, 6-2, 6-2 with six service breaks. Tomic landed 75 percent of his first serves but Federer still won 48 percent of the points off Tomic's serve.
No. 11-seeded Juan Martin del Potro ran past Philipp Kohlschreiber 6-4, 6-2, 6-1 with at least two breaks in each set. He didn't face a break point after the first set.
Federer owns a 7-2 series edge over del Potro going into their quarterfinal match. One of del Potro's wins over Federer was a five-set victory in the finals of the 2009 U.S. Open. Nadal is 10-3 versus Berdych, including taking the last nine meetings.