The 18-year-old showed poise and composure that belied her age to come through two tight, grueling sets and outlast her more experienced opponent 6-3 6-4.
“I didn’t expect to be here at all,” Raducanu told reporters after her win. “I mean, I think my flights were booked at the end of qualifying, so it’s a nice problem to have.
“I’m just really enjoying the experience. Out there on the court today, I was saying to myself: ‘This could be the last time you play on Ashe, so might as well just go for it and enjoy everything.’
“I didn’t compete for 18 months, but here I am, and it just shows that if you believe in yourself, then anything is possible.”
Remarkably, Raducanu is yet to drop a set in her eight matches at the US Open — five in the main draw and three in qualifying — and is the first qualifier in history to reach the final four at Flushing Meadows.
She will now face 17th seed Maria Sakkari on Thursday, with little more than 24 hours to recover, for a place in Saturday’s final.
When asked how she maintains such composure in high pressure moments, Raducanu credited the lessons she received from her parents when growing up.
Raducanu then joked that they had been “ghosting” her when she had tried to contact them the day before her win.
“I think that the calmness and the mental strength definitely comes from my upbringing,” she said.
“I think my parents have both instilled in me from a very young age to definitely have a positive attitude on court because, yeah, when I was younger, it was definitely an absolute no-go if I had any sort of bad attitude.
“So from a young age, I definitely learned that, and it’s followed me until now.
“When you’re serving out a match on such a big stage, to go into your first semifinals of a slam, you definitely need a sense of calm to get through that moment, especially I was love-30, and to just reset and focus on what I could control.
“I knew exactly what patterns I was going to play and, yeah, I was just very focused and in the moment. Wasn’t getting ahead of myself.”
Raducanu is the second teenager to reach the semifinals at this year’s US Open after Canada’s Leylah Fernandez beat Elina Svitlolina on Tuesday.