TOKYO — Novak Djokovic’s dream of a Golden Slam ended in the early hours of another thick night at the Olympics, on one last searing winner off the racket of Germany’s Alexander Zverev.

Zverev stormed back from a set and a service break down to beat Djokovic, the world’s No. 1 ranked men’s player, 1-6, 6-3, 6-1, scoring a stunning upset of an all-time great who had seemed nearly invincible lately and well on his way to pulling off a feat no male tennis player had achieved.

Djokovic was trying to win all four Grand Slam tournaments and the Olympic gold medal in a calendar year. He had won the Australian Open, the French Open and Wimbledon and came to Tokyo looking for the fourth jewel. The United States Open takes place at the end of the summer.

Djokovic appeared to be on cruise control when he broke Zverev’s serve to get to within three games of the match in the second set. Zverev swatted a ball skyward in frustration. He appeared destined to meet with a quick end, like Djokovic’s first four victims in Tokyo.

But with little to lose, Zverev began unleashing his booming serve and setting up a series of crushing forehands to take control, and Djokovic started inexplicably spraying his shots off the court.

“Terrible, just terrible,” Djokovic said, when asked how he was feeling at the end of a night that also included a loss in the mixed doubles semifinal.

Djokovic tried to slow Zverev’s momentum with a long bathroom break between the second and third sets, as he has done in tense moments in the past. But it didn’t work and in the two-of-three-set format he did not have the cushion that the marathon afforded during Grand Slam matches, which require three of five sets to win.

After Zverev reeled off eight consecutive games with seeming ease, sprinting to a 4-0 lead in the deciding set, Djokovic faced a mountain too steep to climb, despite several thrilling comebacks he had staged during the first three Grand Slams this year.

“It’s just sport,” Djokovic said. “You got to give him credit for turning the match around. He served extremely well. I wasn’t getting too many looks on the second serve. My serve just drastically dropped. I didn’t get any free points from 3-2 up in the second set. My game fell apart.”

When his last shot flew past Djokovic, Zverev grabbed his face with both hands in disbelief and he embraced the Serbian champion at the net.

Zverev said he told Djokovic he would go down as the greatest player in the history of the sport, that he would win the most Grand Slams and the most Masters titles and spend more weeks as the top player in the world than anyone.

“I knew he was chasing a Golden Slam but you can’t win everything,” Zverev said. “I told him he was the greatest player of all time, but I’m sorry.”

Then he stared at the sky wondering what he had just achieved — the lifelong dream of winning an Olympic medal. He will play Karen Khachanov for the gold medal Sunday.

The upset was all the more surprising because Djokovic had spent the week becoming the pied piper of the Tokyo Olympics, and the strategy seemed to be working.

After he won the Wimbledon singles title this month, Djokovic went home to Monte Carlo and turned off his phone.

He slept. He spent time with his family, and he did some hard thinking about whether he wanted to travel to Tokyo, without being bombarded by messages from Serbian officials, sponsors or anyone else about what he should do.

After winning in front of crowds at the Grand Slams, he hated the idea of playing in nearly empty stadiums in Tokyo, as required by the Japanese government during the coronavirus pandemic. And he worried that the haul to Japan and the oppressive summer heat might wear him down ahead of the U.S. Open starting in late August.

On the other hand, he loves to play for his country and had a rare chance for a calendar-year Golden Slam. Rafael Nadal and Roger Federer, Djokovic’s rivals in the men’s greatest-of-all-time race, had never managed it — and most likely never will.

But there was something else about the Olympics that lured and energized Djokovic, who has always craved the adulation that Nadal and Federer have received.

In the Olympic Village, where Djokovic is not staying but has eaten many meals and spent much of his leisure time, he became the man to be photographed with, or break bread with, or talk about life with, or take an impromptu seminar on sports psychology with, or stretch and work out with. The busy social calendar has certainly not hurt the extensive image overhaul campaign he has been on this year.

No athlete of Djokovic’s stature threw himself into these Games as Djokovic has. Where others saw the tournament as a labor, Djokovic embraced it as a break from the monotony of the tennis tour, an 11-month grind during which tennis players rarely get to interact with athletes from other sports.

On Wednesday, he even signed on to play in the mixed doubles competition with Nina Stojanovic, something few expected him to do. In fact, after losing to Zverev, Djokovic headed almost immediately to Court 1 for his mixed doubles semifinal. He chased down balls and battled late into the night, as he and Stojanovic lost to Aslan Karatsev and Elena Vesnina of Russia, 7-6 (4), 7-5.

“I’m having a lot of fun on the court and a lot of fun in the village,” Djokovic said earlier in the week.

Djokovic’s merry-man of the Games play also served as an image reclamation project for him after an awful 2020. In the spring, when the pandemic was in its first months and most sports were still shut down, he hosted a tennis exhibition with several of his fellow players that became a superspreader event.

He recorded and endorsed a discussion with one of his spiritual advisers, Chervin Jafarieh, in which Jafarieh spoke of how people can make polluted water and toxic food safe to consume through the power of their emotions. (You can’t.)

At the U.S. Open, he swatted a ball in anger that hit a line judge in the throat by accident. He was immediately disqualified.

During the Australian Open, he drew criticism in the country for insisting on amenities for players who were under hard lockdowns because of coronavirus cases on their flights — a move that did not sit well in a country where cases were extremely low and people had hesitations about whether the tournament should be held at all.

But he ended up winning that tournament for the ninth time, then defeated Nadal on clay in Paris and has been on a Grand Slam roll unlike anything in the men’s game in a half-century.

Then, in Tokyo, he became the man about the athletes’ village, doing splits with Belgian gymnasts, talking mental strategy and trading training tips with volleyball players from Turkey, and whooping it up with Team Serbia when a countryman won a medal in taekwondo.

The love came back his way, too. Though center court at Ariake Tennis Park was largely empty Friday, roughly three dozen Serbian coaches and athletes made it sound like a rock star was playing a small nightclub. Through a set and five games, it seemed as if the support would pull him through.

But a rolling Zverev and, perhaps, the pressure of what he was trying to achieve, ultimately proved too much, just as it had for Naomi Osaka, the tennis star who lit the Olympic flame and had the weight of the host nation on her shoulders and lost her third-round match.

Zverev said as he embraced Djokovic at the net, he had nothing but praise for the player who has 20 Grand Slam titles and had a 6-2 record against him entering the match.

“I was thinking that I had a medal for Germany,” Zverev said. “This is probably the proudest moment of my career.” For Djokovic, the weekend will now bring two bronze medal matches, disappointing consolations for a week that had been going so well.

“I feel terrible right now in every sense,” he said. “But tomorrow hopefully is a fresh start, and I can recover and at least win one medal for my country.”