Rotterdam, The Netherlands (SportsNetwork.com) - Top-seeded Andy Murray and No. 4 seed Stan Wawrinka were a pair of opening-round winners Wednesday at the $1.825 million ABN AMRO World Tennis Tournament.

Murray handled French qualifier Nicolas Mahut 6-3, 6-2, while Wawrinka held off game Dutch wild card Jesse Huta Galung 6-3, 3-6, 6-3 at Ahoy Rotterdam.

Last month's Australian Open runner-up Murray was a titlist here in Rotterdam in 2009. He'll next face 24-year-old Canadian Vasek Pospisil.

An upset came in the second round when Luxembourg's Gilles Muller dismissed fifth-seeded Bulgarian star Grigor Dimitrov 6-2, 7-6 (10-8).

In other second-round action on Day 3, Frenchman Gael Monfils upended seventh- seeded Spaniard Roberto Bautista Agut 7-5, 7-6 (7-5) and Ukrainian Sergiy Stakhovsky stifled Austrian Dominic Thiem 6-1, 6-3.

In some other first-round action, Italian Andreas Seppi overcame Dutch wild card Robin Haase 6-7 (5-7), 6-3, 6-3 and Spaniard Guillermo Garcia-Lopez dismissed Uzbekistan's Denis Istomin 7-6 (7-5), 6-4. Last week's Zagreb champion Garcia-Lopez will face Wawrinka on Thursday, while last week's Zagreb runner-up Seppi will encounter third-seeded defending Rotterdam champ Tomas Berdych.

Also on Thursday, second seed Milos Raonic will take on Italian Simone Bolelli.

The 2015 Rotterdam champ will earn $405,000.