Marta Kostyuk spooks Emma Raducanu with scary good upset in Cluj-Napoca

WATCH: Kostyuk maintained her mastery of Raducanu in a 57-minute clinic at the Transylvania Open.

Emma Raducanu surged to the forefront of tennis’ next generation when she captured her maiden major title at the US Open, but even as she rounded back into form at the Transylvania Open, she was wary of ghosts from her not-too-distant past.

“She absolutely destroyed me in the juniors,” the Brit said in previewing quarterfinal opponent Marta Kostyuk. “Every single time.”

Five months older than Raducanu, Kostyuk didn’t remember their quite rivalry like that—to the extent that she remembered it at all—but the once and future wunderkind took heart from the endorsement and channeled it into a scary-good performance to reach her third WTA semifinal of the season, 6-1, 6-2.

“I felt like, ‘If she remembers it like that, I have to go with it,’” the 19-year-old said after the 57-minute match. “But I don’t remember it! I don’t remember ‘killing’ her…”

She continues after flashing a wry smile.

“Killing her on the court, that is. Then I saw our head-to-head was 1-1, so it wasn’t really like I’d been destroying her.”

It was a bit rough for me to watch both of their runs. I’m trying to be the best I can be, so I obviously want to be where they are, and I’m sure it’s going to happen soon. It just didn’t feel very nice to watch them playing a final...It left a footprint on my brain, and was motivating me not to stop. Marta Kostyuk

Kostyuk had a vague memory of an ill-fated racquet deal contributing to her lone loss to Raducanu, but with little more to go on, she set to work in the hopes of undoing the game that had flummoxed seven experienced opponents en route in New York.

“When you watch tennis and when you play someone are two very different things. I was watching, but I felt like Emma came on court and no one could really understand how to play her, or how her ball flies, or even her weak sides. It was just tough to figure out, especially when she was playing so well.

“I knew I had just a little bit of time to figure it out,” she added later, “and after the first couple of games, I kind of got it.”

Rolling into the 2018 Australian Open third round as a 15-year-old, Kostyuk has shown flashes of the viciously crafty game that helped her stand out as a junior, but found herself crestfallen to see Raducanu and runner-up Leylah Fernandez suddenly surpass her and play the century’s first all-teen final in Flushing Meadows.

“I have to be honest,” she says after a deep sigh. “It was a bit rough for me to watch both of their runs. I’m trying to be the best I can be, so I obviously want to be where they are, and I’m sure it’s going to happen soon. It just didn’t feel very nice to watch them playing a final. It was very inspirational because it gave me strength and helped me realize that I can do the same thing. This is a thing they gave me, and I’m very thankful for that. Leading something is never easy: when you are the first, there’s always extra pressure and more expectations.”

The result came at the start of a season nadir for Kostyuk, who had already overcome a COVID-19 diagnosis to reach the fourth round of Roland Garros. To edge into the US Open final, Raducanu dismissed Maria Sakkari—ironically the very player to send the Ukrainian packing in the first round.

“It left a footprint on my brain, and was motivating me not to stop. The last couple of weeks were very tough for me: I was struggling with my health, confidence, the way I play, and all these other things.”

She turned disconsolation into determination when she watched good friend Paula Badosa storm to her first WTA 1000 title at the BNP Paribas Open and clinch a WTA Finals debut.

“Paula had a very consistent year, which is very impressive because it’s not a big thing in women’s tennis right now,” she mused. “I’m very lucky to be close to her, and we can both share how we’re feeling and what’s going on. I was very, very happy for her, and I hope she can win the WTA Finals. I’m going to cheer for her!

“All these results, it’s like, I was always feeling like I still don’t belong in the Top 100 even after making it there. All of these wins that are happening now, they’re coming from people close to me, and so it gives me confidence and strength that I can do it, as well. These are real people who are my friends, and I talk to them and know they have their struggles, but they can still win. This obviously helps.”

From losing five of six matches between the US Open and the inaugural WTA 250 in Tenerife, she is yet to drop a set this week at the spookily-themed 250, and will next aim to avenge another haunting loss, this time to Simona Halep from Indian Wells earlier this month.

“Now, I feel like things are falling in place, and I’m trying to use it as much as I can, and hoping to get this title.”

Playing in the heart of Transylvania with a Halloween final in sight, Kostyuk will have to go "Boo!" or go home.