“I don’t really have the champion mentality yet, which is like someone that can deal with not playing 100 percent,” Osaka conceded in a confessional news conference. “I always have wanted to be like that, but I guess I still have a long way to go.”

Williams is in a different position, agonizingly close to familiar territory.

When Williams left the tour to give birth to her daughter, Olympia, she was still close to the peak of her powers: she won her 23rd major singles title at the 2017 Australian Open without dropping a set while two months pregnant.

Since her return to competition in February 2018, she has reached four Grand Slam singles finals at an age when nearly all of tennis’s great champions have already retired.

But she has lost all of those finals, often playing well short of her best against inspired opposition. She has been beaten soundly by establishment figures: Angelique Kerber at Wimbledon in 2018 and Simona Halep at Wimbledon in 2019. She has lost convincingly to new stars who grew up watching her win on television: Osaka at the U.S. Open in 2018 and 19-year-old Bianca Andreescu at the same tournament in 2019.

Friday’s defeat belonged in a different category, considering that Williams had overwhelmed the 27th-seeded Wang by the no-nonsense score of 6-1, 6-0 in the quarterfinals of the U.S. Open just a few months ago. Wang, a free swinger with power and speed who plays mainly from the baseline, bore no resemblance to the player who looked trapped in the spotlight at Arthur Ashe Stadium in September.

The power gap has indeed closed with Williams’s opponents, although her first serve does remain a singular weapon, but only when she places it properly. Against Wang, Williams landed just 56 percent of her first serves.

Still, the intimidation factor has also diminished and the bonus points that go along with it. Unlike last summer, Williams converted just one of six break points against Wang Friday.