Rafael Nadal was bundled out of the Gerry Weber Open by defending champion Philipp Kohlschreiber in Halle while five-time winner Roger Federer was pushed to the limit.
Defeat for Nadal ended a 13-match winning streak which saw victories in Rome and Roland Garros, and gave world number 34 Kohlschreiber his first win over the Spaniard in nine attempts.
Kohlschreiber was on top from the start, dominant behind his first serve and giving Nadal only three break point chances, all of which he saved. The German broke Nadal once in each set to win 6-3 6-4 in 86 minutes.
Federer was forced to endure his second consecutive final set tie-break against young Canadian Milos Raonic before prevailing 6-7 (7-4) 6-4 7-6 (7-3) to book his place in the semi-finals.
Federer, who beat Raonic in similar fashion in Madrid less than two months ago, dropped behind after a tight first set devoid of break points, but clinched the second after earning a single break.
After neither player once again failed to fashion a break point in the deciding set, Federer stepped up to sweep through the tie-break and finally wrap up victory in one minute short of two hours.
Federer will face Mikhail Youzhny in the last four after the Russian shrugged off the embarrassment of his one-sided French Open defeat to David Ferrer by beating Czech veteran Radek Stepanek 6-4 4-6 6-4.