On a day in which three other seeded players fell, the top seeds won handily. Only Murray, seeded second, dropped a set Thursday.
Del Potro, the top seed and defending tournament champion, took out Paul-Henri Mathieu 6-3, 7-6 (7-2). Del Potro had 10 aces, equaling the number of points he lost on serve in the match.
Murray eliminated qualifier Dominic Thiem 6-4, 3-6, 6-3. Thiem had a break in each of the first two sets but Murray didn't allow him a break opportunity in the third, winning 70 percent of the points on serve.
Berdych, the No. 3 seed, didn't lose his serve in a 6-4, 6-3 win over Nicolas Mahut. He lost a mere nine points in his 10 serving games.
But Philipp Kohlschreiber claimed a 7-5, 7-5 upset of fourth-seeded Richard Gasquet while Jerzy Janowicz ousted No. 6-seeded Tommy Haas 6-4, 6-4 and Ernests Gulbis beat eighth-seeded Grigor Dimitrov 6-5, 7-6 (7-3).
The final match of the day saw Igor Sijsling routed Michael Berrer 6-1, 6-2 with five breaks.
Marin Cilic, who beat fifth-seeded Jo-Wilfried Tsonga, claimed a quarterfinal spot with a win Wednesday.
The formal name of the event is the ABN AMRO World Tennis Tournament.
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