Former world No.1 Novak Djokovic's US Open has ended with this earliest Grand Slam exit in two decades as he fell to Mariano Navone 7-6 (7/5), 5-7, 4-6, 6-2, 6-1 on Sunday.

The defeat scuppered the Serbian tennis legend's latest bid for a 25th Grand Slam title, and ended a streak of 78 Grand Slam first-round victories, which began at the 2006 French Open.

Considering the obvious discomfort the 39-year-old Djokovic began feeling early in the match, it was truly impressive that he managed to take Navone, 25, the distance.

After battling through more than four and a half hours in the Arthur Ashe Stadium, Djokovic gracefully congratulated his opponent.

"I don't want to take too much out of his win. Congrats to him. He's a nice guy, a fighter," Djokovic said of the 25-year-old Argentine, currently 48th in the men's rankings.