The semifinals are set after Wednesday's action at the U.S. Open following four quarterfinal matchups.
Below, we'll break down the day's scores, highlights and key moments from another fun day in New York.
No. 22 Frances Tiafoe def. No. 9 Andrey Rublev 7-6, 7-6, 6-4
No. 3 Carlos Alcaraz def. No. 11 Jannik Sinner 6-3, 6-7, 6-7, 7-5, 6-3
No. 6 Aryna Sabalenka def. No. 22 Karolína Plíšková 6-1, 7-6
No. 1 Iga Świątek def. No. 8 Jessica Pegula 6-3, 7-6
Carlos Alcaraz outlasted Jannik Sinner in an instant-classic match that lasted five hours and 15 minutes and ended at 2:50 a.m. ET.
It's the second-longest match in U.S. Open history, trailing only the 1992 men's semifinal between Michael Chang and Stefan Edberg that took five hours, 26 minutes to complete.
Alcaraz, 19, is the youngest men's player to reach the U.S. Open semifinal since Pete Sampras won the tournament as a 19-year-old in 1990.
Sinner had a chance to end things much earlier. After winning the second and third sets in a tiebreak, he was up 5-4 on match point in the fourth set. Alcaraz fought back, winning three consecutive games to force a decisive fifth set.
Despite losing the fourth set, Sinner came out strong in the fifth. He was serving with a 3-2 lead, but Alcaraz broke him to even things. The Spanish star rode a wave of momentum by winning the final four games to secure a spot in the semifinal against Frances Tiafoe.
Carlos Alcaraz @carlosalcaraz
What can I say? 🤯 US OPEN SEMIFINALS! Incredible battle <a href="https://twitter.com/janniksin?ref_src=twsrc%5Etfw">@janniksin</a>! You really forced me to improve, and I'm sure we'll have many more matches in the future! 🤝🏻 <a href="https://twitter.com/usopen?ref_src=twsrc%5Etfw">@usopen</a> <br><br>📸 Getty Images <a href="https://t.co/EeR1rzSDkA">pic.twitter.com/EeR1rzSDkA</a>
Tiafoe's magical run continues.
The 22nd seed became the first American man to reach the U.S. Open semifinals since Andy Roddick back in 2006, knocking off Rublev on Wednesday.
It didn't come easy, requiring two tiebreakers, but Tiafoe is through.
And unsurprisingly, he's the fan favorite:
It's been an incredible run from Tiafoe. He's now knocked out No. 14 Diego Schwartzman, No. 2 Rafael Nadal and No. 9 Rublev in consecutive matches, all while dropping just a single set.
It's been the story of the tournament thus far.
He now awaits the winner of Alcarez vs. Sinner in the semis.
On the women's side, Sabalenka—who was banned from Wimbledon this year as a Belarusian national after Russia's invasion of Ukraine, given Belarus' close political ties to Russia—returned to the grand slams and booked her ticket to the semifinals with a convincing win over Plíšková.
"I think I started really well, and the first set was really high level for me and put a lot of pressure on her," Sabalenka told reporters. "First set was really great. In the second set, I knew she would kind of try to come back and she would do better. I just tried to hold my serve and tried to put her under pressure on her serve."
It is Sabalenka's second straight trip to the semifinals in New York. She will meet Świątek, who outlasted Pegula in straight sets 6-3, 7-6.
"I remember when I was an underdog and any match like that was pretty surreal. Right now, it feels a little bit like a routine," Świątek said after the match. "But I'm pretty happy that I have motivation and that I want to push even harder because I think any of us can win any tournament, so anybody is a really dangerous opponent."
Świątek, who entered as the top seed in the tournament, is now the first Polish player to reach the semifinals at the U.S. Open since 1968. She's now 19-2 in Grand Slam matches this year. She is aiming to win the second major singles title of her career.