Novak Djokovic's US Open ended in the first round on Sunday, in a result few would have predicted a few years ago. The 39-year-old was beaten by 48th-ranked Argentine Mariano Navone in a marathon four-hour, 36-minute match, visibly struggling physically for large parts of it.

A brutal five-set battle

Navone won 7-6, 5-7, 4-6, 6-2, 6-1, coming back from a set and a break down to close out the biggest win of his career. Djokovic fought through multiple bouts of nausea, needed an inhaler, took a medical timeout, and was given medication during the match as cramping and back pain increasingly took over.

He'd led by a break in the fourth set before his body started to give out, ultimately taking just one more game for the rest of the match.

Djokovic opens up on what went wrong

Speaking afterwards, Djokovic admitted the whole experience on court had felt awful, describing an ongoing issue he's carried through much of this year involving vomiting and serious physical discomfort, on top of cramping and pain that eventually caused his back to give out.

Asked whether the issue was fixable, he said simply that he was trying, without offering more certainty than that.

The end of an incredible streak

The loss snapped a run of 37 consecutive first- and second-round wins for Djokovic at the US Open, and marked his earliest exit at any Grand Slam in 20 years, since a first-round loss at the Australian Open back in 2006. He made 70 unforced errors over the course of the match.

It wasn't an isolated incident either. Djokovic had needed treatment for a mystery medical issue just two weeks earlier in Cincinnati, also involving vomiting, adding to growing questions about his health heading into the tournament.

A dream win for Navone

For Navone, the win was the realisation of a childhood dream. He described beating Djokovic on Arthur Ashe Stadium as one of the biggest moments of his career, reflecting on growing up wanting the chance to test himself against the sport's most dominant player on tennis's biggest stage.

Whether this marks the end of Djokovic's time at Flushing Meadows remains to be seen.