Iga Swiatek has now won five and lost three of her eigh meetings with Jessica PegulaWorld number one Iga Swiatek lost 6-2 6-7 (4-7) 6-4 to Jessica Pegula in the semi-finals of the Canadian Open.
The match was disrupted in the second set tie-break when the Rednex novelty classic Cotton Eye Joe began blaring out of the court speakers during play.
Reigning French and US Open champion Swiatek produced an error-strewn display against against the American.
"I felt like I was in control. It feels great and there's no better way to earn it, right?," Pegula said.
"She played some really great tennis at the end of the second set and in the third. So, she made me earn it."
22-year-old Pole Swiatek's serve was broken 11 times by fourth-seed Pegula, who wrapped up victory in two hours and 30 minutes in Montreal.
Pegula will face either third seed Elena Rybakina of Kazakhstan or Russian Liudmila Samsonova in Sunday's final.
A chaotic first set opened with five straight breaks of serve before Pegula finally managed to hold to take a 4-2 lead.
The 29-year-old American backed it up with a break against the four-time Grand Slam winner before she served for the set, closing it out with a stunning ace down the middle of the court.
Pegula was on course to win the second set when serving for the match at 5-4, only for Swiatek to force a tiebreak where she rattled off five straight points to level the match to setup a decider.
With Pegula 4-3 up in the breaker, the sound of Cotton Eye Joe's chorus inexplicably burst forth as Swiatek looked set to finish off a smash, leading to the point being replayed.
Swiatek then broke Pegula twice early in the final set to take a 4-2 lead only for her service game to unravel, allowing the world number three to pull level.
A confident service game put Pegula 5-4 ahead and, on match point, Swiatek hit a forehand wide to hand her opponent a spot in the final.
