Novak Djokovic loses US Open opener for first time in his career: What happened?

Noval Djokovic suffered a first-round defeat at the US Open for the first time in his career.

The 39-year-old star was stunned by Argentine Mariano Navone 7-6 (5), 5-7, 4-6, 6-2, 6-1 on Sunday night. The four-hour, 36-minute marathon marked Djokovic's earliest Grand Slam exit since the 2006 Australian Open.

The major reason behind the shocking exit from the US Open was his physical struggle throughout the game. Djokovic battled recurring illness and physical collapse throughout the match, vomiting on court,

The Serb star also experienced cramps and received treatment for back and shoulder pain during a medical timeout.

The 24-time major champion committed 70 unforced errors and admitted he “despised every moment” of the physical struggle he had gone through on the court.

Djokovic said, “It’s something that I’ve been carrying, unfortunately, pretty much every match this year: vomiting, throwing up, a serious issue there. Then my whole body starts to collapse, basically cramping and pain. Yeah, the back just gave up in the end and shoulder, and I couldn’t close it out.”

“Just struggled all the way since the fourth game of the match,” Djokovic said. “When it comes to matching myself and the overall feeling of how I felt with my body and playing, it was really not enjoyable. I pretty much despised every moment that I spent on the court for that.”

He also congratulated Mariano Navone, stating, “"I don't want to take too much out of Mariano's win. Congrats to him, he's a nice guy and a fighter.”

The shocking loss prompted Djokovic to openly question how much longer he can continue playing Grand Slam tennis.