HALLE - Rafael Nadal has lost in straight sets in the Gerry Weber Open quarter-finals to defending champion Philipp Kohlschreiber of Germany.Top seed Nadal was on a 13-match winning run that including a record seventh French Open triumph, but went down 6-3 6-4 to Kohlschreiber in Halle.Kohlschreiber, the eighth seed, will play third seed Tomas Berdych or fellow German Tommy Haas in the last eight.Earlier in the day, Mikhail Youzhny beat Radek Stepanek 6-4 4-6 6-4. Second seed Roger Federer was in action again Milos Raonic of Canada."I said it was going to be tough,” said Nadal. "He plays well on this court. You just have to congratulate him."He played very aggressively, served well, returned well. He played better than me. I was suffering when he was serving. I didn’t have that energy to change the situation.”Nadal confirmed he would now be heading home to Mallorca to rest ahead of Wimbledon, which starts on 25 June."I can’t practice on grass there but it’s better not to practice for a few days. It’s time to rest with my family, friends, to relax,” he added.