France’s Kristina Mladenovic beat former champion Caroline Wozniacki to reach the Indian Wells semi-finals and break into the world’s top 20.
The fast-improving 23-year-old, seeded 28th, saw off 2011 winner and 13th seed Wozniacki 3-6 7-6 (7-4) 6-2.
Mladenovic next faces Russia’s Elena Vesnina, who beat American Venus Williams 6-2 4-6 6-3.
In the men’s draw, Stan Wawrinka reached the semi-finals for the first time with victory over Dominic Thiem.
The Swiss third seed battled for two and a half hours against Austria’s Thiem, seeded eighth, before dominating a tie-break in the final set to win 6-4 4-6 7-6 (7-2).
Wawrinka, 31, will face Spain’s 21st seed Pablo Carreno Busta, who saved two match points to beat Uruguay’s Pablo Cuevas 6-1 3-6 7-6 (7-4).
Mladenovic added Wozniacki to seven-time Grand Slam champion Venus Williams, world number three Karolina Pliskova and, earlier this week, fourth seed Simona Halep on the list of leading names she has beaten in 2017.
She began her quarter-final slowly, falling 5-1 behind against Wozniacki, who was in good form herself after reaching recent finals in Doha and Dubai, and had won all three of their previous matches.
But the Frenchwoman showed why her singles game is beginning to match the level that sees her currently ranked third in doubles.
Her more powerful game began to dominate Wozniacki and, after edging the second set in a tie-break, Mladenovic raced way with the decider as the Dane struggled with an ankle problem.
“I was frustrated with the beginning of the match,” said Mladenovic, who won her first WTA title in St Petersburg earlier this year.
“I was hitting a lot of unforced errors and you can’t do that against a top player like Caroline.
“I felt like I had to adjust to this huge court. It feels different to play out here after hiding out on the small courts. I just tried to stay positive and fight like always.”