Swiss tennis ace Roger Federer suffered a surprise defeat to Croatia's Borna Coric in the final of the Halle Open on Sunday.
Coric, 21, won 7-6 (8-6) 3-6 6-2 to end the Wimbledon champion's run of 20 consecutive victories on grass.
Federer, 36, was bidding to win the event for the 10th time and secure his 99th career title heading into Wimbledon next week.
The defeat means Spain's Rafael Nadal will take over as world number one.
Coric took a little over two hours to claim his first grass court title. This was his first victory over Federer in their third career match.
The 21-year-old Croatian had started the tournament by beating world No. 3 Alexander Zverev of Germany, and finished by denying Federer his 99th career title.
Coric became only the sixth player to defeat Federer in a grass court final, joining Novak Djokovic of Serbia, Britain's Andy Murray, Spain's Rafael Nadal, Germany's Tommy Haas and Australia's Lleyton Hewitt.