World number one Carlos Alcaraz was stunned in the Swiss Indoors Basel semi-finals as Felix Auger-Aliassime set up a final clash with Holger Rune.
Auger-Aliassime saw off the US Open champion in just 82 minutes as he won 6-4 6-3 to take his unbeaten run to 12 matches.
The Canadian was in irresistible form on Saturday, with his shot placement in decisive moments proving far more consistent and lethal than his counterpart, hitting 23 winners to Alcaraz's eight.
Twenty-two-year-old Auger-Aliassime is still fighting to qualify for the ATP Finals for the first time and victory in Sunday's final will move him up to sixth in the rankings having won each of his two previous tournaments in Antwerp and Florence.
"It's amazing," Auger-Aliassime said. "I never expected it, when I was in Florence three weeks ago, or after the US Open. I'm just really happy that all my work is coming together.
"I've always believed that I can play this way, that I can be consistent in that way, but one thing is to believe and the other is to actually do it. It's nice to feel that way, it's nice to come out on the court and win that many matches in a row. So hopefully this is just the beginning of seeing me play this way."
Rune awaits after the Dane beat Roberto Bautista Agut 7-6 (7-1) 7-6 (10-8) despite being 6-2 down in the second-set tie-break. He will move into the top 20 for the first time as a result of that win.
The final of the Vienna Open will be contested by Daniil Medvedev and Denis Shapovalov, who came through their respective semis in straight sets.
Top seed Medvedev was exceptional against Grigor Dimitrov, with the Russian's serve proving especially important in his 6-4 6-2 win.
Medvedev won 87 per cent of points on his first serve to leave Dimitrov frequently struggling for momentum, and the former world number one recognised that impact.
"The serve is probably the most important shot in tennis," he said. "I was lacking it a little bit this season, I was doing too many double faults. Sometimes in important moments my serve could have been a little bit better. I was working a lot with my coach to try and find this rhythm [again], and so far I'm serving good here. I'm really happy about it and that's also why I'm playing so good."
Shapovalov ultimately romped to an impressive win over Borna Coric.
A tight first set was followed by the Croatian getting bageled as Shapovalov won 7-6 (7-4) 6-0 to reach his second final of the year.