Nick Kyrgios sent down 30 aces in losing 4-6, 7-6 (7/2), 7-6 (7/4) to Hubert Hurkacz in a dramatic Halle grass court semi-final on Saturday.
The Australian wild card, who has excelled on the surface over the past fortnight and backed up last weekend's Stuttgart semi-final, was unable to earn victory against the Pole who defeated Roger Federer last year at Wimbledon.
Fifth seed Hurkacz produced 27 aces of his own in a match of more than two hours during which neither man was able to seize any momentum.
Wimbledon semi-finalist Hurkacz, ranked 12th to the 65th of Kyrgios, will aim for his first grass court title on Sunday when he plays Daniil Medvedev.
The world number one dashed the dreams of Germany's Oscar Otte of winning a title on home soil with a 7-6 (7/3), 6-3 victory.
Kyrgios was in good spirits after going down to Hurkacz, whose massive serve rivals his own.
"He's a hell of a player," the Australian said.
"His serve is incredible. I honestly didn't feel like I was getting any sort of read on it.
"I was playing well in the last two sets, but I played a shocking tiebreak in the second set. It is what it is, I'm happy with my form this week."
Medvedev needed 65 minutes to win the opening set, helped as his opponent double-faulted on a set point.
He sealed victory on his first match point after 96 minutes, delivering his eighth ace.
"It was hot (32 Celsius/89.6 Fahrenheit), tough conditions," said Medvedev.
"Reaching the final is not everything, I want to show my best tennis and win the title."
He added: "I'm happy hat I managed to raise my level this year on grass. I love playing on grass."
Medvedev is seeking his first trophy since ending Novak Djokovic's chances for a calendar Grand Slam last September with victory in the US Open final.