NEW YORK — In the latest stunning upset at the US Open, Jessica Pegula took advantage of an off-night for Iga Swiatek to dispatch the world No. 1. The world No. 6 won 6-2, 6-4 in just under 90 minutes to set up a semifinal against Czech Republic’s Karolina Muchova. She is the fourth American to reach the semifinals of this year’s tournament in New York, following Emma Navarro, Frances Tiafoe and Taylor Fritz.

The last time multiple American men and women reached this stage of a Grand Slam tournament was in 2003, also at the US Open. Eventual champion Andy Roddick was joined by Andre Agassi, Lindsay Davenport and Jennifer Capriati.

The victory lifted the sixth-seeded Pegula into her first Grand Slam semifinal. She had previously lost six quarterfinals, including two in each of the last two seasons, while rising to No. 3 in the world rankings and winning WTA Masters 1000 tournaments — just shy of a Grand Slam.

“I’ve lost so many times,” Pegula said from the court when it was over.

As she approached her 30th birthday at the end of last season, Pegula fired David Witt, her longtime coach. He had taken her from outside the top 100 to the top of the sport in five years. Pegula wanted more. She wanted one of those trophies that Swiatek collects like snow globes.

Pegula told herself that if she could just stay in the last eight, the quarterfinals might just come her way. She had missed a golden opportunity at Wimbledon in 2023, leading 4-1 in the final set against Marketa Vondrousova, who had little Grand Slam pedigree and no history of success on grass. She went on to win the whole tournament, as it turned out.

Jessica Pegula is in her first Grand Slam semifinal on her seventh attempt. (Robert Prange/Getty Images)

Now, finally, 15 years into her pro career, she is just two wins shy of her first. She benefited from a flawless performance from the world No. 1, which becomes an unwelcome theme in her rare defeats. When these losses come, Swiatek sprays the ball everywhere but between the lines. She has made 41 unforced errors in 16 matches.

“I wanted to play the way I wanted to play,” she said when it was over, to gauge Swiatek’s level before deciding how small to make her margins. She could tell right away that Swiatek wasn’t playing well and was getting frustrated, especially on her serve. She told herself to attack. “I really made it a point to try to get in and keep doing that the whole time.”

That worked, even in the second set, when Swiatek improved her serve but couldn’t find a rhythm on the floor.

“Normally I can put myself under pressure or fight back, but today I just made too many mistakes,” said Swiatek.

The defeat was the latest misstep for the five-time Grand Slam champion in a frustrating summer. She has been on the losing side of every tournament since her French Open triumph, her fourth Roland Garros title and third in a row. It left no doubt as to her reputation as one of the best female clay-court players of the modern era.

Swiatek has been on shaky ground since leaving her beloved red clay of Paris, losing in the third round of Wimbledon to Yulia Putintseva, in a defeat that resembled a few other defeats, and a little like this one. Even when she briefly returned to clay before the Olympics, she produced a similar performance against Zheng Qinwen in the semi-finals before losing to Aryna Sabalenka in Cincinnati.

The long season has taken its toll on Switek’s body and mind. She earned that exhaustion, having played deep in all the clay-court tournaments she played in the spring, winning three. Since then, the summer has become a drag, with the only consolation being a bronze medal at the Paris Olympics after she lost her chance at gold.

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All the bad losses look essentially the same. Her serve, recently evolved into a more serious weapon, doesn’t get on the court often enough. Her vaunted forehand, a frighteningly efficient shot over the past three seasons, flies wildly off the court. The backhand, usually a stabilizing force, starts to go next, and Swiatek, often one of the game’s great problem solvers, just tries to hit the ball harder, whether it’s short in the court or deep on the baseline, expecting a different result that never comes.

Iga Swiatek’s groundstrokes failed her. (Al Bello/Getty Images)

Pegula remained steadfast in her serve, knowing that Swiatek had pulled rabbits out of her hat and had fallen behind at Roland Garros.
She served and let Swiatek’s errors—including a forehand return that nearly went outside the tramlines after a 65 mph second serve—put her on three match points. Swiatek saved one with a tight forehand winner across the court, then another with an even tighter backhand down the line.

But then, as she had been doing all night, she hit a rally backhand wide and sent Pegula’s arms flying.

Pegula’s victory brought a new star to a US Open that has suddenly become an all-American affair. Tiafoe and Fritz will play each other in Friday’s semifinal, the first all-American semifinal since 2005 and guaranteeing that an American will play in a Grand Slam final for the first time since Andy Roddick’s 16-14 loss to Roger Federer in the fifth at Wimbledon in 2009.

And yet so much of the mountain has been preserved.

In Muchova, Pegula will face one of the game’s greatest natural talents, a player who can float across and across the court like few others when healthy, before scoring points like no other. She has struggled with a serious wrist injury for most of the season, but Muchova has quickly found her form this summer and has yet to drop a set in New York.

Navarro will face Aryna Sabalenka, the two-time Australian Open champion and arguably the best hardcourt player in the world. She has been fierce all tournament and is playing as she did in Australia in January.

For Tiafoe or Fritz, world number 1 Jannik Sinner and 2021 champion Daniil Medvedev are the most likely opponents in the men’s final.

They could all benefit from the possibility that Pegula’s clinical play on Wednesday night was strong enough to make the leap.

“I was able to take advantage of some of the things she wasn’t doing well,” Pegula said.

(Fatih Aktas/Anadolu via Getty Images)