ST. PETERSBURG, Russia - Defending champion Kiki Bertens stayed on course for a second straight title at the St. Petersburg Ladies' Trophy, rounding out the final four by virtue of a 6-4, 7-6(3) victory over teenage Russian qualifier Anastasia Potapova in the quarterfinals.

The World No.8 was pushed hard in her first-ever meeting against the former junior Wimbledon champion, as she was forced to battle back from a 5-2 deficit in the second set and saved three set points. 

"It was a tough battle today. I think she played well especially in the second set," Bertens said after the match. "She kept fighting and going for her shots. I think today wasn't the best tennis from my side, but I managed - I don't know how - to win in two sets. 

"In the second set, we had really long rallies. I had to run a lot and the points were really long. She's a great fighter on the court, so sometimes the points were taking forever, and I was just trying to hang in there."

The two players also traded breaks twice in the opening set before Bertens scored what proved to be the decisive break of serve in the seventh game, as the World No.101 gave the Dutchwoman all she could handle in just her fourth-ever match against a Top 10 player.

Despite the gulf in experience between the two, Bertens was complimentary of her teenage foe after the match: "I think she's already playing really well. She's playing really aggressive and moves well on the court. I think there's a good generation coming up. She has potential, and I think everyone can see that.

The Russian hadn't lost a set en route to the last eight, and seemed on course to win a set against a Top 10 player for the first time in any of those meetings as she won the first three games of the second set. After denying Bertens two chances to break back in the fifth game, Potapova had four chances to extend her lead to 5-1 in a marathon Bertens service game that went to deuce seven times. 

Unable to seal an insurance break against the World No.8, the 18-year-old stayed level-headed and nonetheless held with ease, but after she failed to convert the first two of her set points on return in the next game, she surrendered serve to love to let Bertens back into the match.

The World No.8 continued to respond well with her back against the wall, as she saved another set point in the next game, and held serve to stay in the set for a third time as she forced a tiebreak. Overall, those set points were three of 14 break points that Bertens saved in the match, as Potapova only managed a conversion rate of 3-for-17.

"I knew it [that she faced many break points] somewhere in that moment," Bertens said. "I think the serving was not great today. I was searching for the rhythm and being aggressive wasn't working well. At the end, it's about [converting] the break points and she wasn't able to do that, so I think I did something good today and I can be proud of that." 

After beating Veronika Kudermetova and Potapova without the loss of a set to advance to the semifinals, Bertens advances to a match against a third straight home favorite, as she'll take on Russian No.1 Ekaterina Alexandrova. The two have never played previously. 

"We'll see how it goes tomorrow. Ir's another Russian, so I think I'll again have the crowd against me," Bertens said with a laugh. "For me, that's all fine. I'm just going to prepare as good as I can for tomorrow and I'm ready for a big fight."

2020 St. Petersburg Highlights: Bertens downs Potapova to round out final four