Rising Canadian slugger Milos Raonic and reigning champion Philipp Kohlschreiber of Germany were among Monday's first- round winners at the $835,000 Gerry Weber Open, a grass-court Wimbledon tuneup.

The fifth-seeded Raonic fired 19 aces past wild card and last year's Gerry Weber runner-up Philipp Petzschner in a 7-5, 7-6 (7-1) victory, while an eighth-seeded Kohlschreiber held off big German/Jamaican wild card Dustin Brown in a pair of tiebreaks, 7-6 (7-4), 7-6 (7-4), at Gerry Weber Stadium.

Kohlschreiber, who was a runner-up here in 2008, bested Petzschner in last year's all-Philipp, all-German finale.

Other Day-1 wins came for German Cedrik-Marcel Stebe, Russian Mikhail Youzhny, Chinese qualifier Ze Zhang and Poland's Lukasz Kubot.

This week's top seeds are French Open champion Rafael Nadal and five-time Halle titlist Roger Federer, who was also a runner-up here in 2010. Both Nadal and Federer will enjoy opening-round byes.