Novak Djokovic, a four-time champion at Flushing Meadows and one of the most successful men's player in Grand Slam history, has been eliminated in the first round by Argentina's Mariano Navone in one of the biggest upsets of recent years.

The Serbian legend lost a gruelling five-set battle 7-6(5), 5-7, 4-6, 6-2, 6-1 on Arthur Ashe Stadium, with the match lasting four hours and 36 minutes. While Navone deserves enormous credit for one of the finest victories of his career, much of the post-match discussion centred on Djokovic's physical struggles and what this defeat could mean for the final chapter of his remarkable career.

For the 39-year-old Serbian, the result is significant for several reasons. It marks his first loss in the opening round of a Grand Slam since the 2006 Australian Open, ending a streak of 78 consecutive first-round victories at major tournaments. It was also the first time in his career that he had lost in the opening round of the US Open after previously compiling a perfect record at that stage of the tournament.

Perhaps most surprisingly, the defeat did not come against one of the sport's established elite players. Mariano Navone arrived in New York ranked outside the world's top 40 and was widely viewed as an outsider. Yet the Argentine showed tremendous resilience, recovering from losing the second and third sets before taking advantage of Djokovic's physical decline in the final stages of the match.

As the contest wore on, it became increasingly clear that Djokovic was struggling physically. The Serbian later revealed that he had been dealing with recurring health problems throughout the season, including episodes of vomiting, cramping and back pain. Those issues became impossible to hide during the final two sets, where Navone dominated and Djokovic appeared unable to maintain his usual intensity.

While no athlete can remain at the top forever, Djokovic's decline has become one of the defining stories of men's tennis in 2026. The pursuit of a record-extending 25th Grand Slam title continues, but opportunities are becoming increasingly limited. The Serbian has now gone multiple majors without adding to his historic tally, and his body appears to be placing greater restrictions on what remains possible at the highest level.

For Navone, meanwhile, this victory represents a career-defining breakthrough. The Argentine not only claimed the biggest win of his career but also became the first player ever to defeat Djokovic in the first round at the US Open. On a night that was supposed to belong to one of tennis's greatest champions, it was the 25-year-old outsider who emerged as the story of the tournament.

The wider significance of Djokovic's defeat also extends beyond a single result. For the first time in more than two decades, a Grand Slam second round will take place without any member of the sport's famous "Big Three" still active in the draw. Roger Federer has retired, Rafael Nadal has stepped away, and now Djokovic's campaign has ended before it truly began.

Whether this defeat proves to be merely a disappointing tournament or another sign that the end is approaching remains to be seen. It would be foolish to completely write off a player who has repeatedly defied expectations throughout his career. However, for perhaps the first time, the questions surrounding Djokovic's longevity seem louder than the questions surrounding his chances of winning another Grand Slam.

At Flushing Meadows, tennis may not have officially said goodbye to Novak Djokovic. But it certainly felt like another reminder that one of the sport's greatest eras is drawing ever closer to its conclusion.