She lost the Australian Open final in January to her younger sister, Serena Williams. This time, with Serena at home in Florida expecting her first child, Venus will face Garbiñe Muguruza, a 2015 Wimbledon finalist who is seeded just 14th here. But Muguruza has punched high above her seeding, displaying the level of intensity and consistency that once earned her the hashtag #muguruthless — though it has been missing of late.

“Muguruza is playing very well,” Witt said. “But Venus is feeling pretty confident coming out of this match with Konta, and I really think if she plays the way she’s been playing, I don’t see Muguruza beating her.”

Konta, the No. 6 seed from Britain, had defeated Williams in three of their last four matches, but Thursday’s meeting was their first on grass. It was a huge-hitting, high-quality and dead-even encounter until 4-4 in the opening set, when Williams faced the first two break points of the match at 15-40.

She saved the first with a backhand winner and then, after missing her first serve on the next, decided to take a big risk: ripping a huge second serve at 106 miles per hour at Konta’s body that caught Konta by surprise, causing her to miss the return.

The bold serve did not only startle Konta.

“I was like, ‘Man! Who does that?’” said Williams’s sister Isha Price, who was watching from the players box.

Witt added: “That second serve was ridiculous. Ridiculous in a good way.”

It also proved pivotal, as Williams held her serve and then broke Konta in the next game to secure the first set — and the momentum for good.

“I don’t necessarily think it was the be-all-end-all, but it definitely took my break point away,” said Konta, 26. “Her being able to do that is why she is a five-time champion here.”