NEW YORK >> Serena Williams already was struggling to keep up in a fast-paced U.S. Open semifinal when she stopped behind the baseline after a third-set point and leaned over. She held that pose for a bit, then clutched at her lower left leg and asked for a trainer.

While Williams took a medical timeout for a tape job for what she later said was an Achilles issue — her latest bid for a 24th Grand Slam singles title seemingly slipping away — her opponent, Victoria Azarenka, sat in a sideline seat, eyes closed, calm and composed as can be.

After a delay of about five minutes at Arthur Ashe Stadium, action resumed, and while Williams raised the force of her shots and volume of her shouts, it was Azarenka who finished off a 1-6, 6-3, 6-3 victory today to return to a major championship final for the first time in seven years.

“Maybe,” Williams said, “I took a little too much off the gas pedal at some point.”

The loss left her just short of the record-tying No. 24 yet again.

She was beaten in the finals of four of the preceding seven Slams, including at Flushing Meadows in 2018 and 2019.

“I mean, it’s obviously disappointing. At the same time, you know, I did what I could today,” said Williams, who has six U.S. Open singles trophies. “I feel like other times I’ve been close and I could have done better. Today I felt like I gave a lot.”

With her 39th birthday a little more than two weeks away, the question will become: How many more chances will Williams get? She did confirm afterward she’ll head to Paris; the French Open starts Sept. 27.

As for the Achilles, Williams said she stretched it while chasing a ball during one of the lengthy baseline exchanges with Azarenka, but wouldn’t blame it for the defeat.

“I don’t think that had anything to do with it,” said Williams, who repeatedly hopped on her feet at the baseline when play returned. “Ultimately, it didn’t affect my play at all.”

In Saturday’s final, Azarenka will face Naomi Osaka in a meeting between two-time major champions who have both been ranked No. 1 in the past and have been by far the two best players since tennis resumed last month after a pandemic-forced hiatus.

Azarenka won the Australian Open in 2012 and 2013 and lost to Williams in the U.S. Open finals those two years.

She’s finally back in a title match at a major.

“How is it different? I mean, mentally, I’m in such a different place. I think seven years ago, after I won the Australian Open and stuff, and playing kind of consistently with good results, it was kind of I wouldn’t say expected but kind of expected for me to be in the final. I don’t think that was the case this year,” said Azarenka, a 31-year-old from Belarus who is ranked 27th.

“But it feels more fun this year, more fulfilling, more pleasant for me,” she said. “It feels nice. Nicer.”

This was Williams’ fourth consecutive three-setter in New York and although she was far better at the outset today, racing to a 4-0 lead inside of 15 minutes, Azarenka eventually did get going.

Evidence of Azarenka’s brilliance: She compiled 12 winners and merely one unforced error in the second set, then continued her baseline mastery in the third, especially with her backhand.

That carried her to her first win against Williams in 11 career Grand Slam matchups between the pair.

After going a full calendar year without a single tour-level victory, Azarenka has won 11 matches in a row. Osaka’s streak is at 10 after her 7-6 (1), 3-6, 6-3 win over Jennifer Brady in a hard-hitting semifinal filled with fast serves and strong forehands.

Two weeks ago, Azarenka and Osaka were supposed to play in the final of the Western & Southern Open — a hard-court event moved from Ohio to New York this year as part of a two-tournament “controlled environment” with the U.S. Open amid the pandemic — but Osaka withdrew because of an injured left hamstring.

“Going to be super fun,” said Azarenka, who sat in her assigned suite in Ashe to watch some of Osaka vs. Brady. “She plays incredible.”

Osaka had her left leg wrapped for her high-quality semifinal on the court where she beat Williams for the 2018 title.

“It means a lot for me. I kind of consider New York my second home,” said Osaka, who was born in Japan and moved to the United States as a child. “I kind of love the atmosphere, even though there’s no people here. I feel like this court kind of suits me well.”

Suited both players just fine.

Osaka served at up to 120 mph; Brady reached 117 mph. And they pounded the ball once it was in play, too, particularly off the forehand side.

“I just felt like I was sticking it out. It felt like we were trading serves,” Osaka said. “I tried to adjust a little bit on her serve in the third set so maybe that helped.”

They combined for 70 winners — 35 apiece — to just 42 unforced errors, each as good as the other, and it took a bit of luck to swing things after 1 hour, 45 minutes.

That’s when, at 2-1 in the third set, Osaka earned her first break point with a backhand that clipped the net tape and trickled over. She was able to convert the chance when she hit a deep return of a 110 mph serve, and Brady’s backhand in response was called long — although a television replay showed it actually caught a piece of the back of the baseline.

Brady did not challenge the ruling.

Ashe is one of only two courts at the U.S. Open using line judges this year; to reduce the number of people on site, the tournament used electronic line-calling in the other arenas.