To fully appreciate the unmasked roars of 2021 at the U.S. Open, it was best to have experienced the silence and vast empty spaces of 2020.

It was the contrast that made such a difference this year in the collective mood.

“The crowd was the third player this year,” said Chris Evert, one of tennis’s grande dames, who played in her first Open in 1971. “The crowds at the U.S. Open have always been like this, but this year they just seemed louder.”

Established stars like Novak Djokovic had missed the noise. Relative newcomers like Emma Raducanu were hearing it for the first time. The fans had missed the experience.

The surprise upon everyone’s return to the tournament was how forcefully the newest generation of rising stars would storm the gates.

Serena and Venus Williams, Roger Federer and Rafael Nadal were absent at once for the first time in 25 years, and though it seemed that void would be much too big to fill, the young players piled in gleefully. With so many stars missing and so much prime tennis real estate available, young Americans like Frances Tiafoe and Jenson Brooksby became fixtures on the main show courts, playing thrilling matches. The Spanish 18-year-old Carlos Alcaraz, playing in his first U.S. Open, reached the quarterfinals and soon had fans chanting “Carloooooos” as loudly as they usually chant “Rafaaaaaa.”

“I definitely think guys are trying extra hard because there isn’t Roger and Rafa,” Tiafoe said. “I see guys foaming in the mouth. Pretty funny to watch. I’m in the locker room cracking up.”

Attendance was down from 2019, the most recent year when fans were permitted to attend. But volume and emotion were up, and the fans who watched from home or streamed back through the gates — after showing proof of vaccination — were rewarded with one of the most exceptional tournaments in tennis’ long history.

At one end of the continuum was Djokovic, 34, one of the biggest stars in global sport, chasing a rare Grand Slam — victories in all four major tournaments in the same year — and the crowning moment of a long career spent in pursuit of his rivals, Federer and Nadal.

At the other end was the women’s singles tournament, which was improbably commandeered by the 19-year-old Leylah Fernandez and the 18-year-old Raducanu.

But both singles tournaments turned out to be surprises. The top-ranked Djokovic was beaten soundly in Sunday’s final, 6-4, 6-4, 6-4 by Daniil Medvedev, the No. 2 seed. Medvedev, a gangly trilingual Russian, had never defeated Djokovic in a best-of-five-set match and was trounced in straight sets when they met in this year’s Australian Open final. But he was the fresher, more reliable player in New York, serving and returning better than Djokovic, who looked weary and off target. At one stage, he smashed a racket in frustration, and at another looked ready to smash a ball in the direction of a ball girl before stopping his swing.

But this was still No. 1 vs. No. 2 for the trophy. Both Fernandez and Raducanu were unseeded, and Raducanu had to qualify for the main draw. But they surprised more experienced players round after round, in very different fashion, to set up perhaps the most improbable women’s singles final in the four Grand Slam tournaments. Raducanu, playing in only her second major tournament, prevailed on Saturday, but the players will long be linked for the spirit they conveyed together.

Their appeal snowballed beyond their home markets — Britain for Raducanu and Canada for Fernandez. Fernandez’s parents have roots in Ecuador and the Philippines; Raducanu’s parents have roots in Romania and China, and on Saturday night Raducanu showed she was made for 21st century tennis stardom when she recorded a video message in fluent Mandarin for the Chinese audience.

But on the ground in New York, Raducanu and Fernandez’s arrival on center stage created a sense of discovery and wonder. One long shot in a U.S. Open women’s final is rare enough, but two long-shot teenagers made it a scene.

“There was a pent-up desire of people wanting to get out and wanting to experience events in person and time with family and friends and just to celebrate human greatness,” said Ellen Cummings, a fan from New Canaan, Conn., on Sunday before the men’s final.

“I really turned out this year for Novak,” she said, “but the women’s tournament was like this unbelievable bonus. What Raducanu and Fernandez did was such a surprise and such a delight to watch.”

There has been much to bemoan of late and professional tennis has hardly been immune: from quarantines and isolation to Naomi Osaka’s existential crises that have often left her in tears in news conferences as she strained to manage her public role and private struggles in a sport she plainly excels at but that seems to bring her little delight at this stage.

But the 2021 U.S. Open brought a sense of renewal and a sense that, in spite of it all, some of the kids were more than all right, able to summon the energy and optimism to take center stage and make the shots that mattered most. They lit up the largest tennis stadium in the world and then read the room beautifully, with Fernandez hitting just the right note as she talked about New Yorkers’ resilience on Saturday, the 20th anniversary of the Sept. 11 attacks.

“We’ve witnessed such heaviness and pressure in the last year,” Evert said. “Such expectations and intensity and these two girls brought joy.”

Youth, at this U.S. Open at least, was not wasted on the young, but the veterans reveled in the experience, too. On Sunday, Samantha Stosur, a 37-year-old Australian, won the women’s doubles title with her partner, Zhang Shuai of China, over the teenage Americans Coco Gauff and Caty McNally, two more young players full of hope and promise.

It was a return to Arthur Ashe Stadium for Stosur, who won the 2011 U.S. Open singles title, upsetting Serena Williams in the final. Stosur is now very near the end of her career and has long been on the road, away from her family, because of the pandemic-era travel restrictions that make it difficult for Australians to return home.

“This year has been tough for everyone,” Stosur said. “This is the last two days of a trip that’s going to be four months for me away from home. I haven’t done that for a long, long time. To be going home with this trophy just means the absolute world to me. It makes everything worth it.”

Stosur, like several other leading Australian players, did not make the journey to New York last year because of the pandemic. She had seen this year’s U.S. Open billboards with the slogan “The Greatest Return.”

“Absolutely on point for this event this year,” Stosur said.

David Mihm, a Djokovic fan from the small city of Eveleth, Minn., who had never attended a professional tennis match, bought a ticket for the men’s singles final after Djokovic won the penultimate leg of the Grand Slam at Wimbledon.

“Right after the Wimbledon final, I thought this is going to be a once-in-a-lifetime opportunity, and I’ve got to just go for it in case he does make it,” Mihm said.

“I guess I was waiting for something real special,” he said.

He did not get a Djokovic victory, but he did get something special. This U.S. Open, full of surprises and full of life, spilled over with signs of renewal and tennis’s bright future.

Even Djokovic, who came one victory short of the sport’s ultimate achievement, chose not to end on a down note. A year ago, he had eliminated himself from the U.S. Open, inadvertently striking a lineswoman in the throat with a ball he hit in frustration after losing his serve early in his fourth-round match against Pablo Carreño Busta. Djokovic was defaulted from the match, played in an all but empty Arthur Ashe Stadium.

Long the villain in New York, he returned this year, fighting his way through a series of intense tussles on the same court, gradually hearing more and more crowd support as he worked his way to the final. Microphone in hand, he made his appreciation clear through the disappointment on Sunday.

“You guys touched my soul,” he said. “I’ve never felt like this in New York.”

He was hardly alone in that sentiment this year at the U.S. Open, a tournament that felt all at once, both smaller and bigger than itself, and tennis too.