Women's top seed Iga Swiatek survived a scare against American Danielle Collins to reach the Olympic tennis singles semifinals after her opponent withdrew in the deciding set at a hot and humid Roland Garros on Wednesday. Collins withdrew due to cramping stomach muscles and dehydration.

The 23-year-old from Poland, an overwhelming favorite for gold in light of her four French Open titles, was rattled and stunned by a fierce ball to the body early in the third set, but composed herself to earn a 6-1, 2-6, 4-1 victory.

It was not vintage Swiatek by any means, but she lived to fight another day as the first Polish player to reach the semifinals at an Olympic tennis tournament.

The clay court specialist will face China's Zheng Qinwen for a place in the gold-medal match after Zheng outlasted German veteran Angelique Kerber in a three-set thriller.

Swiatek cruised through the opening three rounds and was in total command after a fast start against eighth seed Collins, but her game suddenly went off the boil in the second set as Collins became the aggressor from the back of the court.

Things did not start well for Swiatek in the third set, who was off-balance at the net. Collins drilled a groundstroke that caught Swiatek in the midriff. the American walked around the net to check on her opponent.

But it was Collins who began to suffer in the decider and had one visit from the trainer before calling it a day for medical reasons.