Defending champion Novak Djokovic followed Carlos Alcaraz out of the door at the US Open as he suffered a shock defeat by Alexei Popyrin in the third round.

Australia’s 28th seed Popyrin stood with his arms aloft as he wrapped up a surprise 6-4 6-4 2-6 6-4 win to hand Djokovic his earliest US Open exit in 18 years.

The Serb will end the year without winning a Grand Slam for the first time since 2017, while his search for a record 25th major title goes on.

Djokovic was far from his clinical best, serving a career-high 14 double faults in a Grand Slam match and committing 49 unforced errors.

“I have played some of the worst tennis I have ever played.

“Honestly, the way I felt and the way I played from the beginning of this tournament, third round is a success,” the 37-year-old said.

Djokovic’s exit follows that of French Open and Wimbledon winner Alcaraz, who lost to unseeded Dutchman Botic van de Zandschulp in the second round.

He said he “spent a lot of energy” winning Olympic gold – his self-proclaimed “biggest sporting achievement” – earlier this month.

“I tried my best, I didn’t have any physical issues. I just felt out of gas, and you could see that. From the first match, I just didn’t find myself on this court.

“Life moves on. I’ll try to recalibrate and look forward to what’s next,” Djokovic added.

Popyrin, 25, will make his first fourth-round appearance at a Grand Slam when he faces Frances Tiafoe, who moved past fellow American Ben Shelton in a five-set thriller.

In another game, Frances Tiafoe reached the semi-finals of the US Open in 2022 – his best performance at a Grand Slam

Earlier, Tiafoe avenged his defeat by Ben Shelton at last year’s US Open by beating the 13th seed in an all-American five-set thriller.

The pair, who are good friends, faced each other in the quarter-finals in New York last year with Shelton emerging as the victor.

But it was the lower-ranked Tiafoe who won on Friday, coming from behind twice to triumph 4-6 7-5 6-7 (5-7) 6-4 6-3 after more than four entertaining hours on Arthur Ashe Stadium.

“Ben is an incredible player, he really is. He goes for all kinds of shots, he’s got no care in the world. It’s really annoying,” 20th seed Tiafoe said.

Meanwhile, American 12th seed Taylor Fritz continued his perfect run in New York with a 6-3 6-4 6-2 victory against Argentina’s Francisco Comesana.

Fritz, who has yet to drop a set, will face Norway’s Casper Ruud, a finalist in 2022 who made a remarkable comeback from two sets down to beat Shang Juncheng of China 6-7 (1-7) 3-6 6-0 6-3 6-1.

Russian sixth seed Andrey Rublev was the first men’s singles player to make it into the fourth round with an assured 6-3 7-5 6-4 victory over Czech Jiri Lehecka.

Rublev, a 10-time Grand Slam quarter-finalist who has yet to win a major, will face Grigor Dimitrov after the Bulgarian ninth seed claimed a dominant 6-3 6-3 6-1 win against Dutchman Tallon Griekspoor.