Alcaraz was the subject of one of the tournament’s biggest upsets when he was dumped out by world number 76 Botic van De Zandschulp on Thursday night.
And 24 hours later, defending champion Djokovic joined him in leaving New York early after 28th seed Alexei Popyrin won 6-4 6-4 2-6 6-4 in the third round.
Defeat for Djokovic means it is the first time since 2017 he has not won a grand slam title and is his earliest exit at a major since the Australian Open that year.
It extends the Serbian’s wait for a record-breaking 25th grand slam title and, at 37, his domination may be coming to an end.
Djokovic was scathing of his performance, saying: “He definitely played better and deserved to win.
“I mean, on my end, honestly, the way I felt and the way I played from the beginning of this tournament, third round is a success.
“I have played some of the worst tennis I have ever played, honestly, serving by far the worst ever.”
He continued: “If you play on a quick surface like this without the serve, without ability to win free points there, very low first-serve percentage, many double faults, then you can’t win.
“You can’t win, especially against the guys who are in form like Alexei who is serving big, puts a lot of pressure on your service game.
“It was just an awful match for me.”
He came into the tournament at Flushing Meadows knowing he would be up against it owing to his emotionally draining Olympic win and being without a hard-court match since March.
It is perhaps no surprise that all three players who finished on the podium in Paris have lost early in New York, Alcaraz and bronze medallist Lorenzo Musetti also heading out.
“Obviously it had an effect,” Djokovic admitted. “I spent a lot of energy winning the gold, and I did arrive to New York just not feeling fresh mentally and physically.
“But because it’s US Open I gave it a shot and I tried my best.
“I didn’t have any physical issues. I just felt out of gas, you know, and you could see that with the way I played.”
For Popyrin this was the win of his career and third time lucky against Djokovic, having lost at the Australian Open and Wimbledon.
There was also a nice bit of symmetry about his victory as it inflicted Djokovic’s earliest US Open defeat since 2007 when he lost to Lleyton Hewitt, who was sat in Popyrin’s box.
He said he took inspiration from Dutchman Van De Zandschulp beating Alcaraz.
“I was asleep so I actually didn’t see any of the match, but I woke up this morning and showed my girlfriend straightaway in shock,” the Australian said. “It was crazy.
“Results like that happen. I thought to myself, why not me today?
“I think the way I composed myself and the way I tactically played the match, that was up there with one of the best matches that I have played.”
He continued: “There is countless times when he’s come back from two sets to love down, and I didn’t want to be one of those moments where Novak kind of stepped up and came back.
“That was going through my head.”