On a suffocating night in New York City, Coco Gauff—playing in her first Grand Slam semifinal, and all of 19 years old—fought herself, fought her opponent, and fought a surprise break in the match caused by climate protesters, to win her tense match against Karolina Muchova of the Czech Republic, 6-4, 7-5, and advance to Saturday’s final, marking the arrival of a new American player prepared to take women’s tennis into its future. 

None of this analysis can be called hyperbolic. The full Gauff was on display in New York City, and it’s really something to behold. To wit: Gauff got off to a lightning start against Muchova, racing to a 5-1 lead in the first set. Gauff was on serve, ready to make swift work of this first stanza. She won the first point with her most impressive shot of the match, up to that moment— she’d one-up it later on—a lunging lob that she tucked right in front of the baseline, drawing loud cheers from the partisan crowd.

But Gauff is still 19, and her inexperience showed. With every bit of momentum in her favor, she lost concentration and moxie, and let Muchova back into the match. Gauff inexplicably gave her opponent new life, and Muchova took ample advantage. She broke Gauff, held serve, and then Gauff sent a weak shot into the net to give Muchova another break, and cut Gauff’s advantage to 5-4. 

Gauff, however, reached down deep to quell a disaster. She may be 19, but she’s learned how to win: right before the U.S. Open, in August, she clinched the most important tournament victory of her young career, besting Muchova in the final of the Western & Southern Open in Cincinnati. She’s won nine straight matches coming into this semi. 

And it showed in that final game of the first set: Gauff kept her composure, returned Muchova’s serve and kept the ball in play, allowing Muchova to make all the errors. 

Then, one of the more bizarre moments in the U.S. Open history unfolded. Gauff held serve in the first game of the second set, but suddenly a persistent shouting could be heard from the upper level of Arthur Ashe Stadium. A group of spectators protesting climate change disrupted the event: security was able to remove three of the protesters, but a fourth one affixed his bare feet to the floor. Police officers and medical personnel surrounded the protester in the stands: in the chaos in the crowded halls of the stadium, security guards ordered fans to clear a path, even though they were scrunched together, some trying to capture the scene on camera phones, others filling the beer and food lines during the delay.

Gauff and Muchova retreated to their locker rooms. After about 10 minutes, Gauff said, she changed clothes and ate a bar. Finally, the fourth protester was removed: all four were taken into police custody, according to the U.S. Tennis Association, and in all, it took 49 minutes for play to resume. 

This isn’t the first environmental protest to interrupt a Grand Slam: at Wimbledon in July, protesters stopped play by throwing confetti onto a court. Tennis is an ideal forum for such disruption: since fans have to stay silent between points, those who want to shout, like the protesters Thursday, stand out. Plus, the game is played outside, in increasingly hotter temperatures. Arthur Ashe Stadium was a Thursday night sweatbox. Tennis can expect more of these kinds of delays going forward.  

After the match, Gauff said she expected some kind of protest at the U.S. Open, given the action at Wimbledon, but admitted she would have preferred a disruption not come in the middle of her match, when things were going her way.

“I wanted the momentum to keep going,” says Gauff. “But hey, if that’s what they felt like they needed to do to get their voice heard, I can’t really get upset.” 

Perhaps bolstered by the break, in the second set the rallies started to increase in length, and the level of performance, from both players, started to rise. Gauff finally broke Muchova to go up 5-3, with a chance to serve out the match. Gauff got to match point, but a backhand winner from Muchova at the net saved it for her, and an unforced backhand error from Gauff gave Muchova life. 

Once again, Gauff would have to pull this out the hard way. With Muchova serving, trying to force a tiebreaker, Gauff couldn't take advantage of four more match points. The frustration, however, didn’t stop Gauff from winning the point of the match: back at deuce, Gauff won an incredible 40-shot rally. When Muchova left a drop shot a little too long, Gauff rushed in and slapped a forehand winner past her. The crowd of 23,859 erupted. 

“I know I had the legs and the lungs to outlast her in a rally,” says Gauff. “It was whether I had the mentality and the patience to do it. So 10-15 shots in, I was like, ‘well, this is going to change the match.’ I knew that if I could win that really, that next match point was going to go my way.”  

Gauff was correct. She would not come down from this high. And Muchova couldn’t recover from losing the marathon point: on Gauff’s sixth match point, Muchova left a forehand long, putting Gauff into the final. Gauff screamed and waved and put her hands to her ear, inviting more noise. New York complied. 

Gauff said she was off to watch some anime after the match. “I’m trying to enjoy the moment, but also knowing that I still have more work to do,” says Gauff. “Yes, the final is an incredible achievement. But it’s something I’m not satisfied with.” 

She can finish the job real soon. 

Write to Sean Gregory at sean.gregory.com.