Unseeded Czech teenager Marketa Vondrousova stunned world number two Simona Halep to reach the quarter-finals at Indian Wells.
The 19-year-old, ranked 61st in the world, beat the Romanian 6-2 3-6 6-2.
Vondrousova has already defeated 2017 French Open champion Jelena Ostapenko and last year’s finalist Daria Kasatkina during her run in California.
“I was running a lot – I felt like I was dying for a moment,” Vondrousova joked in an on-court interview.
“I’m so happy to be through and so happy with my play.”
She will play either Ukraine’s Elina Svitolina or Australian Ashleigh Barty in the last eight.
It is the first time Vondrousova has beaten a top-five player.
She served for the match at 5-1 in the third set but was broken to 15, before a scrappy game from Halep ensured her victory.
French Open champion Halep, who is still without a permanent coach, has not won a WTA title since the Canadian Open in August.
Canada’s Bianca Andreescu, 18, continued her remarkable season with a 7-5 6-2 win over China’s Wang Qiang.
Andreescu, who beat Caroline Wozniacki and Venus Williams on her way to the Auckland Open final in January, has won 23 and lost just three matches this year.
She will play Spain’s Garbine Muguruza next, after the former world number one beat Kiki Bertens 5-7 6-1 6-4.