Novak Djokovic's remarkable Grand Slam streak is over – and in a way the 39-year-old had never experienced before.The Serbian suffered his first-ever defeat in the opening round of a Grand Slam since 2006, losing 7-6(5), 5-7, 4-6, 6-2, 6-1 to Argentina's Mariano Navone at the US Open.It ended a run of 77 consecutive first-round victories at Grand Slam tournaments, but the manner of the defeat was perhaps more concerning than the statistic.Mariano Navone defeats 24-time Grand Slam Champion Novak Djokovic in five sets. pic.twitter.com/BE8Dn3qC8j— US Open Tennis (@usopen) August 31, 2026 Djokovic battled severe physical problems throughout the four-hour, 36-minute encounter, vomiting on court before suffering cramps and eventually struggling to move freely. After falling behind in the fourth set, his body appeared to have nothing left."An awful feeling on the court for me," Djokovic admitted afterwards. "Vomiting, throwing up, a serious issue there. And then my whole body starts to collapse. Cramping, pain."The 39-year-old revealed that the problem has affected him throughout the season and admitted he does not know whether it can be fixed."I'm trying, man, I'm trying. Let's see."##NAJAVA_MECA_9927194##The defeat was particularly shocking given Djokovic's record at the US Open and his run to the Wimbledon semi-finals only seven weeks ago.But the biggest question now concerns what comes next.Djokovic has repeatedly acknowledged how difficult best-of-five tennis has become as he enters the twilight of his career. Against Navone, those concerns became impossible to ignore.As he left Arthur Ashe Stadium, Djokovic turned towards the crowd and formed a heart with his hands.For perhaps the first time in his extraordinary career, the 24-time Grand Slam champion left New York with the future looking genuinely uncertain.##NAJAVA_MECA_9928321##