The 18-year-old showed serenity and calmness that belied her age to reach two tight and grueling sets and outscore her more experienced rival 6-3 6-4.
“I didn’t expect to be here at all,” Raducanu told reporters after winning it. “I mean, I think my flights were booked at the end of the standings, so that’s a good problem.
“I’m really enjoying the experience. Today, on the court, I was saying to myself, ‘This might be the last time you play Ashe, so you could go there too and enjoy everything.’
“I didn’t compete for 18 months, but here I am, and it just shows that if you believe in yourself, anything is possible.”
Surprisingly, Raducanu has yet to stop playing a set in his eight games at the American Open (five in the main draw and three in the standings) and is the first qualifier in history to reach the final four at Flushing Meadows.
He will now face the 17th head of qualifying, Maria Sakkari, on Thursday, with just over 24 hours to recover, to secure a place in Saturday’s final.
When asked how he maintains this composure in times of high pressure, Raducanu credited the lessons he received from his parents when he grew up.
Raducanu then joked that they had been “ghosting” him when he had tried to contact them the day before his victory.
“I think calmness and mental strength definitely come from my upbringing,” he said.
“I think my parents have instilled in me from a very young age to definitely have a positive attitude on the track because, yes, when I was younger, I was definitely an absentee if I had some kind of bad attitude.
“So from a young age, I definitely learned it and it has followed me until now.
“When you’re preparing for a match on such a big stage, to get 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 just reset and focus on what he could control.
“I knew exactly what patterns I was going to play and, yes, I was very focused and right now. I wasn’t getting ahead.”
Raducanu is the second teenager to reach the semifinals of the American Open this year after Canadian Leylah Fernandez beat Elina Svitlolina on Tuesday.
“Show all your qualities to the world”
Patrick Mouratoglou is perhaps best known for being Serena Williams ’coach, but he also knows a thing or two about emerging talent training.
Mouratoglou says Raducanu’s deep races at both Wimbledon and the US Open should make tennis fans, particularly those in Britain, excited about his future potential.
“I’m sure you are [British fans] very excited about Emma, ”Mouratoglou tells CNN Sport.” I would be too, if I were British, and even if I’m not British, I think it’s very exciting. She is a big, young player, who came up all of a sudden at Wimbledon.
“We knew her because we had been in the tennis industry for many years. We knew she had talent, we knew she had potential, but she really has been able to suddenly show all her qualities to the world and it’s always nice to see her.
“I also love seeing those faces of these young players who are suddenly so impressed with what they are able to achieve and that such raw happiness is so nice to see.”
As with any rising talent that emerges on the tour, Mouratoglou says the pressure will eventually catch up with Raducanu and that his future success will be determined by the way he does it.
Still, he believes the freedom with which he plays as a young star, without any pressure on his shoulders, has helped Raducanu exceed even his own expectations at the American Open.
“It’s offensive, it plays without limitations,” he explains. “She doesn’t think — and I said it very positively when you’re young like that — you have your whole career to think and think too much, to rethink,‘ Oh, should I do that? this or that?
“When you’re young like that and you like Emma right now and you’re successful, you just have to go with the flow, hit your shots without any stress, no limitations, opt for your shots and that allows you do things you would never think you could.
“And she’s right at that moment.”