Kristina Mladenovic and Elina Vesnina both caused upsets to reach the semi-final of the BNP Paribas Open in Indian Wells.
Frenchwoman Mladenovic, seeded 28th, fought back from a set and a break down to post an impressive 3-6 7-6 (7/4) 6-2 win over in-form Caroline Wozniacki in their quarter-final.
It is the first time she has reached the last four at a tournament of this standing, while the win also ensures she will break the top 20 when next week's rankings are released after an impressive start to the year.
She said in her post-match press conference: "I went for my game. I went for some variation. I think I played differently at some points, trying to use more the court to make her run, as well, because she was doing that pretty well to me.
"It's been a lot of matches and, to be honest, it's like the longest kind of string of winning matches I had so far in my career.
"It feels great, but in the same time, every day I go out there on the court, it's for moments like that. So I'm not getting too excited. I'm just super satisfied that I am on that kind of stages right now and trying to use my chances and the my opportunities I have."
Waiting for Mladenovic in the last four is Vesnina, whose brilliant week in the desert continued with a battling win over Venus Williams.
Vesnina, seeded 14th, beat top seed Angelique Kerber in the previous round and followed it up with a 6-2 4-6 6-3 success over the veteran.
Williams came back from a set down in all of her previous matches in the tournament and will have had Vesnina worried after she saved four match points, but the Russian eventually got the job done at the fifth attempt.
"I saw all three matches of hers, so when I started losing the second set I was like 'uh-oh'," she said on BT Sport 1. "When she has her game on it is so difficult to beat her because she is so powerful.
"I am really happy to win the third set.
"Kristina is on fire and so am I and I think it is going to be a great match. It's our first time in a semi-final of such a great event so it is a big chance for both of us."