Keys, the No. 19 seed and a two-time semifinalist at Melbourne Park, had won the first set. But Rybakina, who like Keys is a precise winner machine when she is playing the tennis she wants to play, had taken the second by seizing the initiative and playing on her front foot. Halfway to the finish, Keys had become a passive counterpuncher.

Iga Swiatek’s latest lopsided win at the Australian Open came via a 6-1, 6-2 score in the quarterfinals against No. 8 seed Emma Navarro on Wednesday. The No. 2-seeded Swiatek not only has not dropped a set so far in the tournament,