“I hope she takes the title now.”

To do so, Williams will have to defeat Strycova and then the winner of the semifinal between Elina Svitolina of Ukraine and Simona Halep of Romania. Other than Williams, only Halep has reached a Grand Slam semifinal before, and she has done it just once at Wimbledon, in 2014.

Both Svitolina and Halep are established top players — excellent counterpunchers and defenders who have not habitually been at their best on grass. Svitolina, seeded No. 8, defeated Karolina Muchova, an unseeded Czech with a yen for the net, 7-5, 6-4, on Tuesday to reach her first Grand Slam singles semifinal. The seventh-seeded Halep, a former world No. 1 and French Open champion, defeated Zhang Shuai of China, 7-6 (4), 6-1.

Strycova has beaten Williams in doubles. She and her partner, her Czech compatriot Lucie Safarova, knocked Williams and her sister Venus out of the 2016 Olympic tournament in the first round.

In singles, though, Strycova is 0-3 against Williams, and she lost all of those matches in straight sets. The power gap is considerable, particularly when Williams is serving as she has been here. She has a tournament-leading 41 aces, 19 of which came against Riske. Playing without knee pain is not only helping Williams’s movement but also helping her generate pace on her serve through leg drive.

But Strycova is a crafty, all-court player, once ranked in the top 20, who has faced plenty of superior firepower in her long career. She has some of the most silken footwork in the sport and likes to chop the ball and to hit well-disguised drop shots, but she can also redirect opponents’ big groundstrokes effectively.

She proved it again Tuesday, rallying from an early 1-4 deficit in the first set to blunt Johanna Konta’s aggressive game and all but silence a Centre Court crowd eager to support the only British singles player still in contention.

Konta’s nerves clearly played a role in the 7-6 (5), 6-1 loss, just as they did in her semifinal defeat against the unseeded Marketa Vondrousova at the French Open last month. But Strycova’s superior shotmaking and decision making also were critical. She is now the oldest first-time major semifinalist in women’s singles in the Open era.