Aryna Sabalenka and Karolina Muchova find themselves back in Thursday evening's semifinals here for the second consecutive year. 

After losing in six consecutive major quarterfinals, the 30-year-old Jessica Pegula stunned World No.1 Iga Swiatek on Wednesday night and broke through in a big way in the Big Apple. 

With some sparkling wins over defending champion Coco Gauff and Paula Badosa, Emma Navarro is another American through to her first career Grand Slam semifinal.

US Open: Scores | Draw | Order of play

No matter how it plays out, we’re going to have a first-time US Open champion. Let’s make the case for each of the fabulous final four:

Must See

No.2 Aryna Sabalenka vs. No.13 Emma Navarro (7 p.m. ET)

The case for Sabalenka

She’s the favorite to win the title here and is playing in her fourth consecutive US Open semifinal -- the first woman to do that since Serena Williams. Sabalenka is now 48-11 in major hard-court matches, the best percentage (.814) of any currently active player.

How’s that for an air-tight case for the reigning Australian Open champion?

Look no further than her 6-1, 6-2 quarterfinal win over Olympic gold medalist Zheng Qinwen. It was a masterclass in fast, furious tennis. Sabalenka faced one break point (which she defended) and converted four of her own.

Sabalenka is 3-5 in major semifinals, but she won the past two -- on the way to last year’s finals and again in Melbourne. She seems comfortable with her enviable position.

“If you get to the Top-5 level, everyone will take you as a favorite,” Sabalenka said after advancing. “But as I always say, it’s not about being favorite, it’s about how hard you’re ready to fight for it.

“But I’m really glad they take me as a favorite, and I'll do my very best to hold this beautiful trophy.”

They’ve split two previous matches, with Navarro winning earlier this year at Indian Wells and Sabalenka returning the favor at Roland Garros. The secret to winning this one?

“I’m going to try to put so much pressure on her,” Sabalenka said, “and probably try not let her do her stuff.”

Sounds simple, but Sabalenka has the extraordinary tools to do it.

The case for Navarro

No one on the Hologic WTA Tour got to 30 hard-court wins this year faster than Navarro. Not Sabalenka, not Swiatek. 

The 30th was a terrific 6-2, 7-5 piece of work over Paula Badosa in the quarterfinals. The 23-year-old American converted five of eight break point opportunities, and Monday she will vault into the Top 10 of the PIF WTA Rankings for the first time.

Navarro, ranked No.57 a year ago, has been a revelation this year; she came into this event without a single win at the season’s final major -- now, she’s looking for No.6.

After trailing Badosa 5-1 in the second set, Navarro came back to win six straight games.

“I felt like if I could push back a little bit and make her think a little bit on her service game, maybe I could sneak my way back in there,” Navarro told reporters. “I think sometimes you’re out in the court, and you can kind of picture yourself playing a third set. When I was out there, I didn’t picture myself playing a third set.”

That’s simultaneous clairvoyance and confidence -- and no one has more right now than Navarro. She’ll be feeling it on Thursday because she’s beaten Sabalenka in their only previous match on a hard court -- 6-3, 3-6, 6-2 back in March in the Round of 16 at Indian Wells. At the time, it was the biggest win of her career, and it proved that she belonged among the game’s elite players.

Against Sabalenka, Navarro said, she’ll try to “scrap out” some longer points and make her hit one more ball. In beating Coco Gauff and Badosa in back-to-back matches, Navarro has shown unnatural poise.

“Very good backhand and very good forehand,” Badosa said of Navarro. “She has variety in her game, so that’s really important. She’s a very complete player, first of all, and that’s very important when you go to a slam to put your emotions on the side. That's maybe the thing that sometimes I don't handle pretty well.

“She does that really well.”

No.6 Jessica Pegula vs. Karolina Muchova (9 p.m. ET)

The case for Pegula

Seriously, did anyone see this coming? Swiatek was going for her seventh semifinal in a major and seventh straight win over a Top 10 player.

Instead, it was Pegula -- crowding the baseline and rushing the five-time Grand Slam champion by taking the ball exceptionally early -- making some personal history, winning 6-2, 6-4.

“I’ve been so [to the quarterfinals] so many freaking times -- I kept losing,” Pegula said in her on-court interview. “Everyone keeps asking me about it, but I was like, I don’t know what else to do, I just need to get there again and win the match. Thank God I was able to do it.

“Finally. Finally, I can say [major] semifinalist.”

No one is playing better: Pegula has won 14 of her past 15 matches, including the title in Toronto and the final in Cincinnati.

Pegula deserves credit for aggressively changing her narrative. Despite a baseline of success, she boldly changed coaches early this year. After a neck injury forced her to miss the Middle East swing, she didn’t play a single clay-court match following an undisclosed injury.

“When I started on grass, I [had] had a couple of months off,” Pegula said Saturday. “I think in a weird way, it was almost a good thing looking back that I’ve been able to kind of start that part of the year pretty fresh. Even though it was a lot going back and forth with the Olympics and the surface changes and all that.”

Winning this quarterfinal match has to be extremely liberating.

“To do it primetime on Ashe,” she said. “Against the No.1 player in the world, it’s crazy. But I knew I could do it.”

Pegula and Muchova -- the only two players yet to drop a set -- have played only once, a few weeks ago in Cincinnati. Pegula was a 5-7, 6-4, 6-2 winner.

“She’s so good, so talented, so athletic,” Pegula said. “I love how she just doesn’t play, comes back and beats everybody. I know she has a lot of experience going deep in Slams as well.

“I’m going to have to bring my best tennis. I’ll worry about that maybe when I wake up in the morning.”

The case for Muchova

She’s playing with house money -- with a win, she clears $1.8 million; a title is worth twice that.

The unseeded Muchova defeated No.22 Beatriz Haddad Maia 6-1, 6-4 -- making her the first player since Jennifer Brady to reach the semifinals here without collecting a single victory in the year’s first three Grand Slams.

If this all looks familiar -- it is. Last year, the 28-year-old from the Czech Republic won her first five matches before losing to eventual champion Coco Gauff. And then was plagued by a wrist injury that would require surgery and take her out of play for nine months.

She’s now won five straight matches again in New York -- only her sixth event back -- and has yet to drop a set. When she’s healthy, her diverse game is hard to handle. She’s come to net more than any woman, served and volleyed more and, as Haddad Maia will tell you, those myriad slices have a cumulative effect. 

The only glitch? Muchova is fighting a “bug,” which sent her off the court several times. When she returned to the court, she handled the pressure impressively, winning 29 of 37 first serves (78 percent) and suffering only one break.

Over the past four years, Muchova has missed three majors. She’s made the semifinals in four of the 13 she’s played -- in three different Slams. What clicks in these big runs?

“I’d say it’s the feeling and it’s as well the confidence when I hit, basically when I’m aggressive on the court -- hitting winners down the line, going to the net when I feel confident to do that,” she told reporters. “When I started to win those points, they kind of, yeah, gives me the good feeling on the court, and then I trust my shots and I would say then it kind of creates my game.”