Novak Djokovicsuffered a surprising loss in the first round of the U.S. Open Sunday night — and he threw up and broke down in tears during the match.

Djokovic — considered by many to be the best tennis player who ever lived with 24 Grand Slam singles titles — got knocked out by unseeded Mariano Navone in five sets,  7-6 (5), 5-7, 4-6, 6-2, 6-1.

In the fifth set, while down 3-1, Djokovic started tearing up as the crowd tried to cheer him on to victory, but nothing could help the tennis great who’s been struggling lately with health issues.

During the 4-plus-hour match, Djokovic vomited on the court and grabbed his foot after he got a cramp. He also popped some pills given to him by a doctor and received a back massage during a medical timeout.

Navone, ranked No. 48 in the world, didn’t seem one bit intimidated by the tennis legend and played aggressively … blowing Djokovic away in the final set.

After the match, Djokovic said, “I didn’t enjoy myself. I think it was obvious that it was an awful feeling on the court for me.” 

By the way … this is Djokovic’s earliest exit in a Grand Slam in the past 20 years, going back to 2006 when he went down in the first round of the Australian Open.