Bitter exchange in stormy clash

Iga Swiatek was accused of being "insincere" by Danielle Collins (right) after a stormy Olympics clash on Wednesday in which the Pole was left struggling to breathe after being felled by a pile-driver backhand from the powerful American.

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In a tense quarterfinal, Collins retired at 1-4 down in the final set having left the court for a medical timeout.

When the pair shook hands at the net, the 30-year-old Collins exchanged heated words with a bewildered Swiatek.

"I told Iga she didn't have to be insincere about my injury. I haven't had the best experience and I don't really feel like anybody needs to be insincere," said Collins, without elaborating.

"They can be the way that they are, and I can accept that, and I don't need the fakeness." Swiatek said she was puzzled by Collins's criticism.