Another United States Open semifinal had just gone awry for Serena Williams, and Williams’s agent, Jill Smoller, and half sister, Isha Price, were in the corridor inside Arthur Ashe Stadium, leaning against a wall and thumbing their smartphones, oblivious to the fact that they were leaning against a huge photograph of Steffi Graf.
Graf, the long-retired German champion, continues to loom large in the age of Serena Williams. And though Williams still has every chance of breaking her tie with Graf and winning an Open-era record 23rd Grand Slam singles title, she now has no realistic chance of breaking her deadlock with Graf for consecutive weeks at No. 1.
At full force, Williams can still be irresistible, as she proved by winning Wimbledon again in July.
But Williams, who will turn 35 this month, is having increasing trouble with the young this season. The 22-year-old Garbiñe Muguruza of Spain beat her to win the French Open. The 21-year-old Elina Svitolina of Ukraine beat her in the third round of the Olympics, and now Karolina Pliskova, 24, of the Czech Republic, has beaten her for the first time, a 6-2, 7-6 (5) upset in their semifinal on Thursday at the United States Open.
“It’s getting more and more interesting,” said Piotr Wozniacki, the father and coach of Caroline Wozniacki, the Danish star who lost by 6-4, 6-3 to Angelique Kerber in Thursday night’s less surprising semifinal. “The new generation is rising up.”
In the final Saturday, Pliskova will face Kerber, who beat Williams in the Australian Open final in January, and, at age 28, actually will be the oldest woman in the history of the Women’s Tennis Association rankings to make her first appearance at No. 1. She will also be the first German woman since Graf to play in a U.S. Open final.
Williams is hardly finished but for now can only watch and consider her accumulating setbacks. In 2015, she was stunned by Roberta Vinci in the semifinals of the U.S. Open, and then decided to end her season and let her body and psyche heal. If she plays on this fall, no certainty in light of injury concerns in recent weeks, she is quite capable of reclaiming the top spot.
Yet there is no doubt that this has been a downbeat year by her standards. She has won only two singles titles, one of them at Wimbledon, and also failed to win a medal at the Rio Olympics last month.
“I mean this year was not good enough,” said her coach, Patrick Mouratoglou. “Only one Slam. For Serena, it’s not enough, for sure.”
Her career, improbable to begin with, has been full of unexpected twists and abrupt shifts in fortune. Thursday’s semifinal respected that tradition. After playing one of her better and grittier matches of the year on Wednesday night to beat Simona Halep in three sets, Williams appeared to have laid the groundwork for a fine stretch run at the U.S.T.A. Billie Jean King National Tennis Center.
Instead, she got overwhelmed by Pliskova in the first set and then failed to fling open the door to a comeback after she had forced it ajar late in the second set.
Down by 0-3 in the tiebreaker, Williams won four straight points, the fourth after a tremendous scrambling get and lob that rebooted a rally which she soon ended with a backhand winner.
It was the sort of spectacular, emotional point that has often shifted momentum in Williams’s direction for good. But on the very next point, Williams missed a big first serve by a great distance and then double-faulted.
The magic and the momentum were gone.
Pliskova’s coach Jiri Vanek, a former top 100 men’s player from Czechoslovakia who was in an understandably giddy mood after the upset, said he was urging her to do “something stupid” to celebrate.
“I said, ‘You just beat Serena; you are in the final!’” Vanek recounted on Thursday night in his delightfully imperfect English. “And she’s like, ‘Let me be me. Go away!’ And I said, ‘No, come on! Let’s go make some funny!’ And she was like, ‘No, no, no. Be quiet, and let me be.’ She’s happy with her phone. You know the young.”
Williams, who has sometimes faltered in Grand Slam tournaments when obliged to play on consecutive days, as was the case this week, said she was not fatigued after her intense three-set victory over Halep.
“I’m a professional player, been playing for over 20 years,” she said. “If I can’t turn around after 24 hours and play again then I shouldn’t be on tour.”
She did, however, make it clear when pressed that she was not 100 percent.
“I have been having some serious left knee problems,” said Williams, whose biggest concern coming into the Open was a right shoulder injury that had hampered her serving at the Olympics.
Mouratoglou said that she struck the ground with her left knee in the second round and that the knee got “worse and worse” as the tournament progressed.
“Yesterday with the long match against Halep, it went to another level,” he said Thursday.
Though diminished and erratic, Williams was hardly incapacitated. She had that great get in the tiebreaker and her average serve speed was 108 miles per hour, the same as it was against Halep.
Williams has played through plenty of angst and nagging pain in her career and prevailed. Pliskova deserves much credit for handling the moment and beating another Williams sister at the U.S. Open. She saved a match point before defeating Venus Williams in the fourth round, and she beat Serena despite the crowd cheering for her errors and even her double faults.
“For the crowd, it’s not probably the best that I beat both of them in their country, but for me it’s really something special,” Pliskova said. “Obviously the match with Venus helped me not only with the game but with the crowd,” adding that it was her first match on center court.
Pliskova has also managed to turn her season and career arc around after falling out of the top 10. Recommitted this season, she still cracked under pressure in the second round of Wimbledon, losing to Misaki Doi of Japan. After that disappointment, Pliskova decided to skip the Olympics and focus on training and preparing for the United States hardcourt season. The result: a big title in Cincinnati and potentially a much bigger title in New York.
Vanek said he kept telling her in practice, ‘‘You have to play like Serena or like Petra Kvitova, go for the winners, don’t wait for long rallies.”
But her improved movement and improved core strength and body positioning also have played a role. She is 6 feet 1 inch.
Getting low to the ball has been a problem in the past, and one of the training tools she has used to address the issue is a belt with elastic bands that attach to her lower legs and force her to move with her knees bent.
“She has to go on the court like that and play volleys,” said Vanek, bending down in the U.S. Open players’ garden to demonstrate. “And she’s screaming, ‘I need a chair.’”
Bent knees or not, as Pliskova coolly dispatched one of the world’s great athletes, she stood very tall. And now it’s time to step up to her first Grand Slam final.