Roger Federer's bid to win a ninth Halle Open title was ended in the semi-final on Saturday by teenage German Alexander Zverev, who defeated the 17-time Grand Slam champion 7-6(4), 5-7, 6-3.
Reigning champion Federer, on the comeback trail after back problems, was looking to reach the final of his traditional pre-Wimbledon tune-up in Germany for an unprecedented 11th time, but found the big-serving 19-year-old home favourite too formidable.
The Swiss world number three had not lost to a teenager for nearly 10 years since the young Andy Murray beat him in Cincinnati in 2006, which gives an indication of Zverev's considerable potential.
World number 38 Zverev, who had lost to Federer in their only previous meeting in May, dropped just four points on serve in the 39-minute opening set, blasting 14 winners as he took the tiebreak 7-4.
Federer earned a break of serve at 5-5 with a beautiful dropshot in the second set to restore parity but Zverev, the son of a former Russian player with the same name, responded strongly to dethrone the reigning Halle champion.
Zverev will meet the winner of the other semi between Austrian Dominic Thiem and German Florian Mayer.