Rotterdam, The Netherlands (SportsNetwork.com) - Top seed and reigning champion Juan Martin del Potro, former titlist Andy Murray and third seed Tomas Berdych were among Thursday's second-round winners, while a trio of seeds went by way of upsets at the $1.85 million ABN AMRO World Tennis Tournament.

The former U.S. Open champion del Potro defeated Frenchman Paul-Henri Mathieu 6-2, 7-6 (7-2), while the second-seeded 2009 champion Murray struggled to get past Austrian Dominic Thiem 6-4, 3-6, 6-3.

Del Potro beat another Frenchman, Julien Benneteau, in last year's finale and was the runner-up here in 2012.

The former Wimbledon runner-up Berdych blew past France's Nicolas Mahut 6-4, 6-3 on the indoor hardcourts at Ahoy Rotterdam.

On the upset front, German Philipp Kohlschreiber took out fourth-seeded Richard Gasquet 7-5, 7-5, 6-foot-8 Pole Jerzy Janowicz upended sixth-seeded German Tommy Haas 6-4, 6-4, and Latvian Ernests Gulbis dismissed eighth-seeded Bulgarian Grigor Dimitrov 6-4, 7-6 (7-3). Gasquet was last week's runner-up in Montpellier in his native France, while the 35-year-old Haas was fresh off his runner-up finish in Zagreb.

One final second-round result saw wild card and Dutch crowd favorite Igor Sijsling dismantle German qualifier Michael Berrer, 6-1, 6-2.

Friday's quarterfinals will pit del Potro against Gulbis, Murray versus hot Croat Marin Cilic, Berdych against Janowicz, and Sijsling versus Kohlschreiber. Cilic is fresh off his indoor title in Zagreb.