Sebastian Korda and Alexei Popyrin slogged through long, energy-sapping quarterfinals on Sunday to set up an evening semifinal at the ATP Montreal Masters.
Second seed Alexander Zverev was the day's biggest victim as he lost to Korda 7-6 (7/5), 1-6, 6-4 in a delayed quarterfinal.
Germany's former Olympic gold medalist was unable to hold a first-set break of serve and handed over a winning opportunity as he dropped serve at four-all in the deciding set against his American opponent.
Australian Popyrin accounted for a second straight seed with his 3-6, 7-6 (7/5), 7-5 fightback against one of the games biggest servers, Hubert Hurkacz.
Victory took nearly three hours, with his semifinal against Korda scheduled for the evening session.
Zverev, 2017 champion in Canada, missed his chance to produce a 50th victory this season.
With rain this week putting the pre-US Open event behind schedule, the winners were forced to compete twice in the day in hopes of getting the event finished on Monday, as planned due to the Paris Olympic.
Fifth seed Andrey Rublev and Italian Matteo Arnaldi were set for the day's first semifinal.
Popyrin had saved three match points in the third round in beating 10th seed Grigor Dimitrov before dispatching Hurkacz.
"I'm really happy but a little bit tired," Popyrin said after winning with 11 aces. "I have another match in about two hours."
Korda beat Popyrin in their only previous ATP meeting at Kazakhstan two years ago.
Korda is on a career-best win streak of eight straight matches. His victory over Zverev after more than two hours was only his second against a top-five opponent.
He will be competing in a Masters semifinal for the second time in his career.
"This means a lot to me. It has been a tough year," said last weekend's ATP Washington winner.
"I've put in a lot of work so I'm happy with the results. I'm having fun on the court and trying to play aggressive tennis."
The son of a former ATP champion from the 1990s has advanced with minimal play. His first-round opponent retired and he got a walkover in the third round when Casper Ruud fell ill.
"I wish I could have played more matches. But I'm feeling good and that's the most important," Korda said.
"I want as many matches as I can get," he added after notching his 30th win of the season.
Hurkacz had not lost to an Aussie since 2021 in Madrid. The Pole was playing this week less than a month after July knee surgery, with doctors telling him his season was over.
A late break for Popyrin paved the way for the upset.
"I'm really happy but a little bit tired," Popyrin said after winning with 11 aces. "I have another match in about two hours."