Borna Coric ended Roger Federer’s 20-match winning streak on grass, beating him 7-6(6) 3-6 6-2 in the Halle Open final on Sunday.
He also brought to a halt the Swiss maestro’s reign as world number one.
Federer was denied a 10th title in the German grasscourt tournament as Coric handed the 36-year-old his first setback on an otherwise serene road towards defending his Wimbledon title.
The defeat meant that Rafa Nadal will return to the top of the world rankings on Monday.
Coric, playing in his first grasscourt final, showed great mental toughness and determination to fend off two set points before clinching the opening set after 57 minutes.
Federer responded by applying further pressure on Coric’s serve in the second set before converting a break point in the eighth game to force a decider.
The 21-year-old then broke Federer in the sixth game of the final set when the Swiss sliced a backhand long, before claiming only his second ATP title.