Rio Olympics: World No.1 Novak Djokovic cries after he's eliminated by Argentina's Juan Martin in 1st round (photos/video)

World number one male Tennis player Novak Djokovic was left in tears as he was shockingly eliminated in the first round of Rio Olympics by a determined Juan Martin del Potro who beat him 7-6 7-6 .

Novak representing Serbia was shocked by Argentina's Del Potro, who had spent 40 minutes stuck in an elevator in the athletes' village earlier on Sunday.

Djokovic's shock loss also comes on a day when Serena Williams and Venus Williams, reigning Olympic champions, suffered their first ever defeat at the Games in 16 matches.

"This is one of the toughest losses in my career," said Djokovic, who was chasing a first Olympic title.

"Delpo was the better player and he deserved to win. That's sport," Djokovic told reporters.

"In the decisive moments, he just came up with some extraordinary tennis and I have to congratulate him.

"It's very sad and disappointing to go out of the tournament this early but I am glad that a good friend of mine, who has struggled with injuries, has won.

"It's one of the toughest losses in my life and career. The wounds are still fresh."

For Del Potro, this was the sort of night he must have doubted he would ever experience, who cried as he hugged Novak. 

 “It was an amazing match for me,” he said.

“I didn’t expect to beat Novak tonight because I know my situation, I know my problems with my backhand and my wrist, but I played an amazing match, my forehand worked very great, my serve was okay and the atmosphere was great too.

“He is a friend on tour,” said Del Potro of Novak. “He is a great champion. He is a great person, he told me really kind words in the end and I appreciated it a lot.”