Hubert Hurkacz battled back from a set and a break down to beat Casper Ruud 5-7, 6-3, 6-2 on Saturday and reach the Canadian Masters final.
He will meet Pablo Carreno Busta in Sunday's title clash after the Spaniard battled nearly three hours to eke out a 7-5, 6-7(7), 6-2 victory against Briton Dan Evans in the second semi-final.
Hurkacz raced out to a 3-0 lead in the first set before Ruud regrouped, delivering a spinning, 97 mile per hour forehand winner to secure the break and a 6-5 lead.
An unreturnable serve in the next game secured the set for the Norwegian, who threatened to run away with the match when he broke the Pole to open the second set.
But Hurkacz responded with a break of his own and an emphatic overhead winner to take a 4-2 advantage and he levelled the contest at a set apiece with an exquisite drop shot.
In the first game of the decider, Ruud squandered a 40-0 lead and was ultimately broken, which shifted momentum firmly in Hurkacz's favour.
The match felt all but over when Hurkacz smashed a backhand crosscourt winner to go up a double break, pumping his fist in celebration.
"Casper was playing really well. He was the better player for the first half of the match," Hurkacz told reporters.
"I was just searching for opportunities, just trying to take every single opportunity to get ahead in the rally and make him uncomfortable. Obviously serve helped at the end."
Hurkacz has come out on the winning side in five of his six career finals appearances.
"I was fortunate to win the first few finals. But tomorrow is going to be a new match. It's going to be a very tricky one and tough one," he said.
Carreno Busta also had to work hard to secure his passage to the final.
The Spaniard won significant first serve points to claim the first set but Evans forced the decider with his sublime net play in the second.
Having squandered a match point in the second-set tie-break, Carreno Busta dominated the third set winning the final 12 points, including eight on return, to stay on course to be the tournament's first unseeded champion since Argentina's Guillermo Canas in 2002.
Fiery Halep to face surging Haddad Maia in final
Simona Halep dug deep to beat Jessica Pegula 2-6, 6-3, 6-4 to punch her ticket to Sunday's Canadian Open final, where she will face Beatriz Haddad Maia after the Brazilian toppled Karolina Pliskova for her latest win over a marquee player.
Two-time tournament champion Halep got off to a sluggish start and the American took full advantage, wrapping up the 35-minute first set with an ace.
But a loose service game by Pegula early in the second set, capped by a unforced backhand error, gave the Romanian former world number one a 3-1 lead as frustration began to mount in her less experienced opponent.
In the third set, Halep broke at love for a 3-2 lead and hung on to claim her 37th victory of the year despite producing 10 double faults and putting fewer than 60% of her first serves into play.
With the win, Halep will re-enter the top 10 for the first time in almost a year when the new rankings are released on Monday.
"The fire is back," Halep told reporters when asked about moments in the match where she appeared poised to take out her frustration on her racket.
"It's a good sign if I do that... it helps me sometimes. I don't know always if it's good or not. But it helps me."
The popular former world number one, who saved 12 of 17 break point chances, said she got a boost in the match's biggest moments from the vocal support of the fans in Toronto.
"It felt like I was in Romania today," she said.
"They sent a lot of energy. In the tough moments they really pushed me. So I would like to thank them for that. And I'm waiting for them, actually, tomorrow."
HADDAD MAIA SLAYS ANOTHER GIANT
In the other semi-final, Haddad Maia broke the big-serving Czech to open the match and produced two excellent first serves to capture the first set.
Pliskova responded with more aggressive play in the second set, which resulted in a 5-2 lead but Haddad Maia weathered the storm and battled back to force a tiebreak.
In the breaker, Pliskova saved one match point but failed to convert her set point opportunity and double faulted to end the hard-fought affair.
The unseeded Haddad Maia has defeated local favorite Leylah Fernandez, world number one Iga Swiatek and Tokyo Olympics gold medalist Belinda Bencic en route to her first WTA 1000 event final.
Haddad Maia beat Halep in the semifinals of the Birmingham Classic earlier this year, a tournament she went on to win for her lone WTA title.
