Canadian teenager Leylah Fernandez shocked another high-ranked opponent in second seed Aryna Sabalenka to reach the US Open final - where she could face 18-year-old Briton Emma Raducanu.
Unseeded Fernandez, who turned 19 on Monday, won 7-6 (7-3) 4-6 6-4 to edge a tense semi against the Belarusian.
Fernandez, ranked 73rd, had already beaten defending champion Naomi Osaka and fifth seed Elina Svitolina.
Raducanu awaits if she beats Greek 17th seed Maria Sakkari later.
If Raducanu continues her own dream run in New York, the pair will set up the eighth Grand Slam final in the Open Era between teenagers.