Chinese Zheng Saisai produced a first round surprise, beating fourth seed Agnieszka Radwanska of Poland at the Rio Olympic Games here on the opening day of tennis competition

Zheng, who was the last to qualify for the women's singles event on Tuesday following several drop-outs in the main draw, eliminated the world number five 6-4, 7-5 in one hour and 39 minutes on Saturday.

Zheng was the more active side in the match when the 22-year-old, ranked 64th in the world, going to the net and winning 12 points in her 20 attempts, compared to her opponent's 9-18.

Zheng previously only entered the doubles event with Xu Yifan and she was informed of the good news four days after she arrived in Rio while China filled the quota of four in the women's singles.

On another court, Zhang Shuai of China also staged a surprise, beating Swiss 12th seed Timea Bacsinszky 6-7 (4-7), 6-4, 7-6 (9-7) in almost three hours.

"It was very hard for me today as there were ups and downs during the match," said Zhang. "Timea is a very smart and talented player and she never let me win easily. It is unbelievable that I clinched the win after she held three match points. I already gave my all."