Third-seeded Frenchman Jo- Wilfried Tsonga suffered an opening-round upset, while his fellow countryman Gilles Simon posted a first-round victory at the $1.7 million ABN AMRO World Tennis Tournament.
Wild card and Dutch crowd favorite Igor Sijsling took out the former Australian Open runner-up Tsonga in 7-6 (7-3), 4-6, 6-4 fashion. The 2011 Rotterdam runner-up bowed out in two hours despite firing 14 aces.
The fifth-seeded former top-10 star Simon got past German Daniel Brands 7-6 (7-3), 6-4 on the indoor hardcourts at Ahoy Rotterdam.
Other Day-1 upsets came when Romanian veteran Victor Hanescu took out seventh-seeded rising Pole Jerzy Janowicz 7-6 (7-4), 6-3 and former world No. 3 Russian Nikolay Davydenko downed eighth-seeded German Florian Mayer 6-3, 6-2.
Also on Monday, Bulgarian Grigor Dimitrov outlasted Aussie Bernard Tomic 6-3, 3-6, 6-3, Slovak Martin Klizan snuck past Paul-Henri Mathieu 6-4, 3-6, 7-5, and Italian qualifier Matteo Viola overcame Spaniard Marcel Granollers 5-7, 6-3, 6-1.
This week's top seeds are the great Roger Federer and former U.S. Open champ Juan Martin del Potro. The field also features last week's champion in Montpellier -- Richard Gasquet.
The reigning Rotterdam champ Federer will open his stay here against Slovenian Grega Zemlja. The 17-time major champion and reigning Wimbledon titlist beat del Potro in last year's marquee finale and also titled in Rotterdam in 2005.
Del Potro will battle oft-injured Frenchman Gael Monfils on Tuesday.