Emma Raducanu was aiming for the third WTA tour-level win of her career against KostyukEmma Raducanu's hopes of facing her idol Simona Halep in the Transylvania Open were ended by Marta Kostyuk in the quarter-finals.
The 18-year-old US Open champion was comprehensively beaten 6-2 6-1 by her teenage Ukrainian opponent.
Before the match Raducanu described how Kostyuk would "destroy" her when they played at junior level.
Kostyuk will face Halep in the last four after the Romanian thrashed compatriot Jaqueline Cristian 6-1 6-1.
"Honestly I don't know how I won the first game," said sixth seed Kostyuk, who needed only 57 minutes to book her spot in the semi-finals.
"I was 15-40 down, she had advantage, she was serving, and I think that's where everything started - I somehow won that game and I gained this confidence."
End of the road for Raducanu
The tournament in Romania had a special meaning for 18-year-old Raducanu as her grandmother still lives in the country and her father Ian was born there.
Raducanu, who is ranked 23rd in the world, recorded her first tour level win against Polona Hercog on Tuesday, followed by a straight-sets victory over Ana Bogdan two days later.
Against Kostyuk, however, Raducanu could not replicate the stunning form she has shown during her meteoric rise.
The third seed made 41 unforced errors compared to 16 by her opponent - who is just five months older than her.
Raducanu went an early break down in the first set but began to find her range and cope better with Kostyuk's powerful serve.
But any thoughts of a comeback for the Grand Slam winner were dashed in the second set as 55th-ranked Kostyuk dominated to secure a semi-final contest with top seed Halep.
