Sascha Zverev, who looked visibly unwell during his four-set loss in the fourth round of the French Open, said as much in the press conference after the match.
"I'm completely sick. After the match with [Marco] Cecchinato, in the night. Yeah, what can I say, I'm completely sick. I can't really breathe, as you can hear by my voice. I had fever as well. I'm not in the best physical state, I would say," Zverev said. "And I think that had a little bit of an effect on the match, today," he said, chuckling sarcastically.
Zverev presented a timeline where he felt symptoms after a match on Friday night, had a temperature of 38°C (100°F) on Saturday night, and still decided to go ahead with his match on Sunday. He did not make clear when he had his last COVID-19 test, because he was mad at the reporter asking the question, the New York Times' Ben Rothenberg. "There's no chance I'm answering your questions after what you've been writing about me in the last past months," Zverev said. For reference, in those months Zverev was caught partying in the French Riviera after spending time in a confirmed coronavirus cluster. Very cool.
There are plenty of thorny questions about how to conduct oneself in a pandemic, requiring a great deal of deliberation and research. Probably, "Should I partake in this professional sports event with shortness of breath and a 100°F fever?" is not one of those questions. That's a straightforward answer. Zverev even said later that he "shouldn't have played," and yet he did. Maybe athletes aren't incentivized make these decisions for themselves, but someone must, to uphold even the barest pretense of caring about public health.