PARIS, France – World No.1 Serena Williams survived a scare from No.60 Yulia Putintseva, while No.58 Kiki Bertens of the Netherlands continued her incredible run in Paris, stunning No.8 seed Timea Bacsinszky.

Kiki Bertens puts cancer scare behind her: Confession time: Heading into the quarterfinal round of Roland Garros, there was only one permutation of results that was going to leave me truly shocked in Paris. Yulia Puntintseva beating Serena Williams? I could understand that. Tsvetana Pironkova beating Samantha Stosur or Shelby Rogers beating Garbiñe Muguruza? I could see a situation where that could happen.

But Kiki Bertens knocking out No.8 seed Timea Bacsinszky in straight sets to make her first Slam semifinal? No, that one I did not see coming. Neither did Bertens. Or her family. On match point she fell to the ground in disbelief, stood up, and looked at her box, which was full of family and friends.

She shrugged.

“I was like, Can you believe it?” Bertens beamed, while speaking to reporters. “Because I cannot. And also my parents were like, No, this is not happening.

“But, yeah, it is.”

Yeah. It is.

On yet another cold wet day in Paris, Bertens became the first Dutch woman since 1971 to advance to the French Open semifinal, beating Bacsinszky, 7-5, 6-2, to score her 12th consecutive win. She’ll face World No.1 Serena Williams on Friday. Behind in much of the first set, Bertens battled back from a break down time after time until she was able to reel off the last three games to take the set. She continued her roll in the second set, racing to a 4-0 lead, before holding off Bacsinszky for the win.

“The circumstances were really tough,” Bertens said. “The court is really slow. The balls are heavy. It’s really tough to play aggressive, and especially with Timea. She is like changing a lot, like with some slower balls and some higher ones, so it was pretty tough for me.

“But I think afterwards I was 4-2 down, and then I was just like, Okay, we are just gonna be calm and try to fight for each point. I did it and I won the first set.”

It sounds so simple. It’s been anything but.

“The last two years were pretty hard for me,” Bertens said. “First I had my ankle surgery and afterwards I had some issues with my health, so that was like pretty tough two years. But since this season we worked really hard to be healthy again, to be fit again. So, yeah, I feel really good now.”

It was a year ago here at Roland Garros, after a 6-1, 4-6, 6-2 first round loss to Svetlana Kuznetsova, that Bertens gave a tearful interview to the Dutch press revealing a cancer scare that had plagued her for over a year. According to the Dutch press, Bertens went in for a WTA health exam during the Miami Open in 2014 and a WTA physiotherapist discovered a lump on her thyroid gland.

Bertens sought out tests in the Netherlands but continued to play for over a year not knowing if the lump was cancerous or not. She had scheduled surgery on the lump after the French Open that year but after a miracle run to the fourth round as a qualifier, she canceled the surgery for fear of the risks.

The stress led to sleepless nights and anxiety. She told Dutch reporters that she was resigned to the idea that she had cancer, trying to prepare herself for the worst. But the uncertainty continued to eat at her. It wasn’t until last year, right before Roland Garros, that she got the green light. She had done a test in America and the lump was benign. The tears she shed with reporters were tears of relief and joy. She could finally move on.

“Now I can start again at zero,” she said last year at Roland Garros. “Stress does so much with your body. I have not slept for a year.”

But Bertens’ struggles didn’t end there. Due to the stress of the cancer scare she was unable to train at an elite level and her fitness slipped. She struggled to get through matches for the rest of the year. She lost 6-1, 6-0 to Petra Kvitova in the first round a few weeks later. With her ranking outside the Top 100, she played mainly on the ITF Circuit, popping up only a the tour’s lower level events.

Last September she hired Raemon Sluiter, a former ATP player, as her new coach. Their off-season priority was to get her back to a top-level of fitness.

“In the preseason I did a lot of work,” Bertens said. “Like the first three weeks was only physical practices, like two, sometimes three times a day. It was hell really, but I’m really glad we did it. Like with my whole team we were like working every day like really hard.”

The hard work has paid off. Along with a new diet – she doesn’t eat carbohydrates in the evening and says she’s sleeping better and has more energy in the mornings – Bertens looks as fit as ever. It’s translated directly into her game. When the tour transitioned to her favorite clay, the wins began to come in bunches.

She beat Caroline Garcia and Kristina Mladenovic in Fed Cup, then proceeded to make the semifinals of Rabat, where she had match point to make the final but lost to Marina Erakovic.

“I had match point there I [lost] the match and in my head I was so stressed and all the time and we were like talking with my coach after that match for so long. I think after that match I just was so calm in my head and just trying to go out there every day and just give everything and then just do my own thing. I think that’s the most important thing.”

Then came Nürnberg. Playing the week before the French Open, Bertens won the title as a qualifier, her first trophy since Fes in 2012. Heading into the French Open only Samantha Stosur had more clay court wins than Bertens this year. Back in action immediately in Paris, she scored the biggest win of her career, beating No.3 Angelique Kerber in the first round and has since knocked out Camila Giorgi, No.29 Daria Kasatkina, No.15 Madison Keys, and now No.8 Bacsinszky.

“Mentally I feel pretty good,” Bertens said. “But physically, yeah, it was tough today out there. I think I had some problems with my calf today, so especially in the second set it was really hard to push off with the serve.”

Her physically state will surely be tested against Serena. Bertens took a medical timeout after the first set against Bacsinszky to get her calf taped. Regardless of how the match turns out, this has been the most surprising of fortnights for Bertens.

Bacsinszky undone: Timea Bacsinszky has spent much of the last two months adapting to the conditions and her opponents. But she couldn’t solve the puzzle of Kiki Bertens. The Swiss struggled in the heavier conditions and simply couldn’t execute her game plan to keep Bertens off-balance.

“The conditions, they were heavier than yesterday,” Bacsinszky said. “I was really struggling with my ball length, so I couldn’t really find a good spot to bother her. Well, she was probably having also a great momentum.

“So I think we played kind of equal all the first set. I mean, I could have won also those games. It could have gone either way. And it was the same in the second set, too. So congrats to her, because she she was able to win the important points.”

After the match, Bacsinszky pointed out that she hasn’t been as in the zone as people think.

“People think, Okay, you get to win many matches and it’s like, Oh, just playing too good and you’re just feeling it. Last year I was mentioning two matches that I had my eyes shut and everything was going in. But all year long, like this year, it didn’t happen yet for me to have such a match. So many times I was feeling kind of not that well in the match but I was able to turn it around.

“Luckily for me it doesn’t happen quite often that I cannot turn it around, but this time I really couldn’t.”

Serena Williams fends off The Feisty One: To paraphrase Andy Murray after the 2012 Wimbledon final, “She’s getting closer.” Yulia Putintseva had twice taken Serena Williams to a first set tie-break only to see the American run away with the match in straight sets. This time Putintseva played a fantastic match to keep Serena off-balance, taking the first set 7-5 and earning break point late in the second set for a chance to serve out the match, only to see Serena roar back to win, 5-7, 6-4, 6-1 in the quarterfinals.

“I think I have more experience now, because I played two times before with Serena on the big courts,” Putintseva said. “This time I was just more confident when I was serving for a set. I was just not thinking. I was just doing it and it went well.”

As for Serena, it wasn’t her best day. It was a frustrating performance from the American, who is trying to defend her French Open title and match Steffi Graf’s Open Era record of 22 major titles. “I just was not playing my best,” Serena said. “I kept missing, just misfiring. Honestly, at one point I didn’t see the light at the end of the tunnel. I guess I was not the most positive mentally, but obviously I didn’t want to stop.”

Despite coming so close to a massive upset – she was just five points away from the win and joked afterwards that a couple of let-cord winners would have sealed it – Putintseva took nothing but positives from her performance.

“I think the match was very close and very far from being on my side,” Putintseva said. “I was trying to do everything what I can, to run, to cover, to attack when I can, to go forward. But it just was unlucky situation end of the second set for me. But it’s okay. I mean, still have some years to play Grand Slams.”

Simultaneous Semifinals Set for Friday: Starting at 1pm it will be Serena vs. Bertens on Court Philippe Chatrier. Garbiñe Muguruza vs. Samantha Stosur will also start at 1pm on Court Suzanne Lenglen.

In the doubles, the semifinals are also set. No.5 seed Caroline Garcia and Kristina Mladenovic take on Margarita Gasparyan and Svetlana Kuznetsova, while No.7 seeds and 2013 champions Ekaterina Makarova and Elena Vesnina play Barbora Krejcikova and Katerina Siniakova.

All photos courtesy of Getty Images.