Barbora Krejcikova ended the dream run of 16-year-old Mirra Andreeva on Sunday to set up an Australian Open quarter-final against defending champion Aryna Sabalenka.
Andreeva hammered sixth seed Ons Jabeur in the second round and then had to save a match point against Diane Parry in round three.
But she ran out of road in her last-16 tie on John Cain Arena against her Czech opponent, who lost the first set for the third time at the tournament before coming through 4-6, 6-3, 6-2.
“I’m fighting,” said Krejcikova, who had lost her previous two matches against the young Russian.
“I’m just trying to give my best and go for every single ball.
“I think I was really improving with every single ball and I was going for it point by point.”
Both players struggled to hold serve in the opening set but Andreeva made the crucial break in the ninth game and served out to love.
The players swapped breaks early in the second set but Krejcikova broke again in the sixth game, going on to level the match.
The Czech player, 28, was again on top early in the deciding set and she broke again for a 5-2 lead, serving out comfortably to reach her second Australian Open quarter-final.