Roger Federer must wait until 2019 for another chance to reach 100 career titles after semi-final defeat by Alexander Zverev at the ATP Finals.
Zverev, 21, tipped by many as a future Grand Slam champion, triumphed 7-5 7-6 (7-5) at London's O2 Arena.
The German claimed victory in the tie-break with a wonderful backhand winner.
He will face Novak Djokovic or Kevin Anderson, who play later on Saturday (20:00 GMT) in a re-run of this year's Wimbledon final.
More to follow.