BEIJING, China - Unseeded Daria Kasatkina sent defending champion and No.11 seed Agnieszka Radwanska out of the China Open on Wednesday, 4-6, 7-5, 6-2.
In the first career meeting between the two players, the 20-year-old came from a set down to oust last year's champion and reach her second quarterfinal at a Premier Mandatory event in her career.
She previously reached the last eight at the BNP Paribas Open in Indian Wells a year ago, falling to Karolina Pliskova.
"It was a great night, a great match," Kasatkina said. "We played a good match and I'm so happy that I won this battle."
A marathon two hour, 32-minute encounter saw little to separate the two players for the duration of the match, as Kasatkina struck 42 winners to Radwanska's 33, and broke serve a total of eight times.
Though she moved ahead by a break in the seventh game of the first set with some finely-carved dropshots and angles, the Russian was unable to see her advantage through to a one-set lead as Radwanska reeled off the final three games.
After a streak of four consecutive breaks to begin the second set, neither player could push the other to deuce or to a break point on return, until Kasatkina engineered a 0-40 lead on Radwanska's serve at 5-5 as she looked to force a decider.
Kasatkina converted on her third break point chance, and served out the set to love as Radwanska buried a backhand return in the net.
The 20-year-old's momentum continued well into the final set, as she broke Radwanska in each of her first three service games to see her way to an advantage she would never relinquish en route to her fifth Top 20 win of the season.
With a spot in the final four on the line, Kasatkina advances to face Simona Halep in a rematch of their second round encounter from the Dongfeng Motor Wuhan Open, which the Russian won, 6-2, 6-1.
"We're going to play for the fourth time, I think, so I'm excited about this match," Kasatkina said of playing Halep, against whom she is 1-2 overall. "It's already quarterfinals, so I have to give my best."