In a tournament of upsets, Thursday’s two quarterfinals at the China Open reverted to the norm, with heavily favored players defeating opponents from outside the PIF WTA Rankings Top 100.

On Friday, it was back to the unnerving and unexpected in Beijing.

Beijing: Scores | Order of Play | Draws

Karolina Muchova ended Aryna Sabalenka’s 15-match winning streak in a dramatic contest that approached three hours. Later, 17-year-old Mirra Andreeva -- defying a stadium jammed full of Chinese fans for the longest time -- pushed Olympic gold medal winner Zheng Qinwen to the absolute limit. Zheng won a thriller in two and one-half hours.

Muchova’s the lowest-ranked player left in the draw -- by far, at No.49 -- and the lowest-ranked to advance to the Beijing semifinals since Monica Niculescu did it 13 years ago. This is only the seventh tournament she’s played since returning from wrist surgery.

“If you had asked me three months ago when I just started to play, I had no idea which way it’s going to go,” Muchova said afterward. “I did semis in States [US Open] and here.

“It’s crazy.”

Welcome to your China Open semifinals. We make the case for each of the four participants.

No.5 Zheng Qinwen vs. Karolina Muchova

The case for Muchova

Call it what you wish -- guts, grit, moxie, determination, fortitude -- Muchova’s got tons of it. Against Sabalenka, she saved two set points in the first frame and, trailing 4-2 in the third, won the last four games.

It was her third straight win over the World No.2.

Muchova posts third straight win vs. Sabalenka to make Beijing semis

“I’m happy I went for it at the end of the first set,” Muchova said. “I was just trying to fight for every ball. It was worth it at the end. I’m glad I picked up the win.”

Hard to believe the 28-year-old from the Czech Republic has only won a single career title (five years ago in Seoul). She reached the 2023 final at Roland Garros and the semifinals of the US Open the past two years. Coming off her third consecutive win over a Top 5 player, Muchova’s aiming for her second WTA 1000 final.

And she’s still not at 100 percent -- the comeback hasn’t afforded her much of an opportunity to work on her fitness. But Muchova’s athletic and startlingly diverse game has carried her this far.

“I’m really happy that I’m back on tour and I can play these big matches,” Muchova said. “Not too shabby.”

Muchova won her first match against Zheng, two years ago in Madrid. But back in July, Zheng was a 6-4, 4-6, 6-2 winner in the Palermo final.

“Tough battle,” Muchova said of Zheng. “She’s serving really well, moving really well. It’s semifinals, you’re not going to get an easy match.”

One thing to keep in mind: Only World No.1 Iga Swiatek has a better winning percentage this year on hard courts than Muchova’s 11-2 (84.6 percent). A win over Zheng will push her past Swiatek.

The case for Zheng

Playing in front of a rabidly partisan crowd comes with a lot of pressure, and so far Zheng has been more than up to it. She’s now reached the semifinals in three of her four career main draws in China, following Zhengzhou and the WTA Elite Trophy in Zhuhai last year.

Down 4-2 in the third set against Mirra Andreeva on Friday, the 21-year-old won the last four games of the match. The final was 5-7, 6-0, 6-4. It was her second consecutive comeback win -- she turned around her fourth-round match after losing the first set to Amanda Anisimova.

That resilience is becoming something of a signature trait for Zheng. At the recent US Open, she dropped the first set in her first two matches, to Anisimova and Erika Andreeva, and roared back to win, eventually making it to the quarterfinals.

“When I was down, I would just focus point by point,” Zheng explained. “When I lost the first set, it was only a couple of points. In the second set, I made some changes. I was more consistent, with better serves, a higher percentage. I got more excited in the second and third sets.”

Zheng will have to clean up her service games if she wants to beat Muchova. Andreeva feasted on her second serve, breaking her six times.

She showed some creativity, however, under heavy duress. Serving at 3-4 in the third set, Zheng unleashed a dropshot to draw even and rolled out another one in the pivotal break of Andreeva that followed. The thumping offerings that have served her so well resurfaced in the final game with two unreturnable serves.

Zheng has produced a 12-2 record at WTA tournaments in China, the best mark of any woman since the year 2000 (minimum 10 matches, excluding the Olympics). In her home country, she’s a perfect 9-0 against players ranked outside the Top 20.

No.4 Coco Gauff vs. No.15 Paula Badosa

The Case for Gauff

This was the 20-year-old American after advancing to the semifinals with a 2-6, 6-2, 6-2 comeback win over qualifier Yuliia Starodubtseva:

“I was just trying to find my groove out there. There’s a lot of things I’m working on. For me, just trying to trust the process.

“I’ve been kind of treating this like practice, to be honest with you.”

Wait -- what? Approaching a WTA 1000 quarterfinal like practice? Maybe that’s the way to view a victory that brought her an additional $175,000 and 167 ranking points beyond the round before. She’ll need to tap into that mindset against Badosa.

Gauff is in a state of flux after failing to defend her US Open title, falling to Emma Navarro in the fourth round. She has a new coaching team -- Matt Daly and longtime counselor Jean-Christophe Faurel -- looking to instill the attacking confidence that carried her to a major last year.

This is Gauff’s second consecutive semifinal at the China Open and her third berth in that stage of a WTA 1000 this year. Hard courts are her happy place; only Aryna Sabalenka (33), Emma Navarro (30) and Iga Swiatek (29) have won more matches on that surface this year than her 26.

And while she’s been quick to downplay her progress in Beijing, Gauff admits that “when you’re in the moment, everybody wants to win.”

The history between Gauff and Badosa is, well, interesting. They’ve become good friends over the years and actually practiced in advance of the tournament. Badosa has won three of five matches, but Gauff took the most recent meeting, 5-7, 6-4, 6-1 in the fourth round at Rome.

Badosa bests Zhang in Beijing, makes fifth career WTA 1000 semifinal

The Case for Badosa

Down a set in the US Open quarterfinals, Badosa was leading Navarro 5-1 in the second set and was three points from leveling their match. Badosa has never been to a major semifinal and that was evident when Navarro -- enabled by a slew of unforced errors -- came back to win the match in straight sets.

“I can’t play, I can’t play,” Badosa told her coach, Pol Todeo, during that match.

That loss stayed with Badosa, who said she was still sad when she arrived in Beijing. After an entire month off, she’s moved steadily through the field, highlighted by a straight-sets win over No.2 seed Jessica Pegula.

“It was very painful for me, especially the way that I lost,” Badosa said of New York. “It’s not very common for the player I am. In the moment, was a very big deal for me and I didn’t know how to handle it.

“I was talking with my coach and he said, `Keep working and it will come.’ In my case, you learn through experiences. Sometimes it’s painful, but it’s the only way.”

Badosa has a few distinct advantages over Gauff. Momentum, at the moment, is her friend. Badosa has won 28 of her past 35 matches and is through to her third semifinal in five events. And then there’s the head-to-head: 3-2, in her favor. Additionally, Badosa holds a 2-1 edge in hard court matches.

This is Badosa’s fifth semifinal in a WTA 1000; her only WTA 1000 title came three years ago in Indian Wells. She’ll draw on that New York experience in an attempt to make her second final at this level.

“She’s done so many things at a young age and I really respect her so much,” Badosa said of Gauff. “That’s going to be a very tactical match. Who will play the important points better, who will serve better? These are the matches that I want to play.”