“I’m sure she’s going to get up soon as well, but she’s just lost a little bit of confidence right now,” Karolina said. “So many matches which I won, she lost them in the third set. Some were from match point, which is really sad, and you just feel a little bit down. I just think she needs some matches to win, and then she will feel better and play better as well.”

The twins, who used to share a coach and travel together to tournaments, text each other frequently. But they speak via Skype for their most important conversations.

“Guys,” Karolina said with a laugh. “We have to talk about this every day. And then, of course, tennis.”

The seventh-ranked Eugenie Bouchard of Canada, who competed against both Pliskova sisters as a junior, has a twin sister of her own, Beatrice. Their shared time in tennis was short-lived.

“My twin sister started with me when I was 5, and she retired at 6,” Eugenie Bouchard said. “I never had the chance to think about, ‘Oh, this would be cool if we could travel on tour together.’ It ended pretty quickly for her.”

Image Kristyna, left, and Karolina Pliskova after winning a doubles title in Hong Kong last year. Credit... Xaume Olleros/Agence France-Presse — Getty Images

But she expressed relief, that she and her sister had not chosen the same track in life. “We already get compared to each other as it is,” she said. “So if we did the same work in life, it would be even worse. I think she would hate it just as much as I do.”