Prior to this week at the Volvo Car Open, Spain's Paula Badosa had never before beaten a Top 20 player. Now, she's scored a win against the World No.1.

The 23-year-old Spaniard's career week on Charleston's green clay continued on Friday night as she upset top seed Ashleigh Barty, 6-4, 6-3, to reach the semifinals at the WTA 500 event. 

The victory is Badosa's second over a seeded player this week, after she ousted No.5 seed and World No.12 Belinda Bencic in the second round.

The former French Open junior champion served seven aces and broke Barty's serve five times, out-acing the WTA's leading server in the process. The World No.71 is the lowest-ranked player to beat Barty since September 2019.

"My coach and I had been talking a lot this morning and [I was] trying to focus on myself," Badosa said after the match. "I know I’m playing the World No.1, and she’s an amazing player, but I’m on a clay court, I know how to play on clay courts, I like to play on clay courts.

"I knew I had to focus on myself, and of course, if she was better than me today, that could be a possibility, so I’d just have to accept it. But at least I tried to do my game, my serve, my forehand, my backhand, and focus on me, and that’s what I did."

Badosa saved a stunning 12 of the 14 break points she faced over the course of 76 minutes, and set the tone early as she saved a pair in her first service game of the match.

Barty nearly drew level in the opener after falling in a 5-2 hole, twice building 0-40 leads as Badosa served for a one-set lead. Though she successfully broke serve in the eighth game, she was unable to repeat the feat in the 10th, and Badosa finally secured the opener after nearly three-quarters of an hour.

"I had a game plan, and I changed it a little bit because I didn’t know how she played, exactly. Of course, I’ve been seeing her a lot of times before, but I never played against her, so I didn’t know exactly how the ball was going to come," Badosa assessed.

"I was quite intense with returns. I knew I had to be, because she serves very good, she changes the serve a lot, she mixes it up, so I knew I had to be very focused on my returns. Then, of course, I think I served very well.

"That was the key of the match, because I [was] a lot of break points down, but then I could do a good serve, so I am quite happy about that. I think that I was intense on the first two or three balls against her, and I think that was very important today."

The two players traded breaks in the first two games of set two, and each denied the other two break chances in the fifth and sixth games, respectively. It was then that Badosa pulled away, riding the momentum of her hold for 3-3 to ultimately win the last four games of the match.

"She’s an amazing player. At the beginning, maybe I was a little bit surprised by the forehand, it was quite fast, and she served very well, and the slice doesn’t bounce, so it was quite tough for me to get used to her game," Badosa continued.

"She plays unbelievable. But I’m quite happy. I think when you play a player like that, the energy on court is different... your nerves are another thing. But I enjoyed every moment on court, and now I’m even happier that I could win."

Though Barty nearly doubled Badosa's total of winners in the match at 34 to 19, she also hit twice as many unforced errors as the Spaniard, 24 to 12.

"I think when you play a player like that, the energy on court is different... your nerves are another thing. But I enjoyed every moment on court, and now I’m even happier that I could win."

- Paula Badosa on her first career victory over a Top 10 player and World No.1.

For a place in the final, Badosa will face No.15 seed Veronika Kudermetova, who ousted 2016 champion Sloane Stephens, 6-3, 6-4.

The Russian World No.38 has not dropped a set in four matches this week, and more than tripled the American's total of winners in the one and 33-minute quarterfinal encounter to reach her second semifinal of the season.

"I really like to play on the clay because I think I have a lot of time to do what I want," Kudermetova said on-court after the match.

"It's the first time I beat a player who's won a Grand Slam and I think that's really important for me. I tried to play aggressive and not give her time, and I think that was the key for this match."

Kudermetova jumped out to early 3-0 leads in each set, and never allowed the 2017 US Open champion to gain a foothold in the match.

The most crucial stage of the match came in the middle of the second set, where Stephens had three break points to level at 3-3, which would've seen her erase a double-break deficit. Kudermetova held strong on serve, however, and was never again threatened through the end of the match.

Badosa and Kudermetova have played twice, and the Russian has won both matches. That includes a 6-4, 4-6, 6-1 victory in the round of 16 in Abu Dhabi in January, where Kudermetova reached her first career tour-level singles final.