Kasatkina also beat Ostapenko in the third round of last year’s U.S. Open and defeated Garbiñe Muguruza, the 2017 Wimbledon champion, on her way to the final in Dubai last month.

In the background, a reporter struggles to include all four individuals within the frame of a battered Android device. This moment is an indication of the snowballing success of Zabiiako and Kasatkina ...