But Williams is still here, just two rounds away from matching Margaret Court’s elusive record of 24 major singles titles.
“People always say you’re not to do something at a certain age, but with technology and time, we can kind of make that age a little longer,” she said.
Williams is 0-4 in Slam finals since returning to the tour in early 2018, several months after childbirth. To get a fifth opportunity, she will need to get past Azarenka. Williams, with her formidable serve clicking and a big head-to-head edge, will be the favorite, but she has not played consistently well enough to be the favorite in the tournament. Osaka, who will face the American newcomer Jennifer Brady in the semifinals, deserves that label as long as her hamstring injury does not resurface.
Williams’s victory over Pironkova did not appear to be as draining as some of her previous matches this summer, but it came at a dangerous time. Williams has had a day off between each of her matches at this U.S. Open, but she will not get that luxury for the semifinals.
Recovery will be critical. Her U.S. Open loss in 2016 came in a semifinal without a day of rest.
At least Williams played the early match on Wednesday, starting slowly as Pironkova sliced forehands, punched flat backhands, hit perfectly disguised lob winners and hustled into the corners to extend rallies and sow seeds of doubt in her more accomplished opponent.
“Definitely, I was feeling it a little in my legs,” Williams said. “For whatever reason, an hour in, I get more energy.”
But Williams, even without the same range or aura she has had in previous years, remains a supreme competitor and unmatched server. She smacked 20 aces on Wednesday, but she also got gritty and countered Pironkova’s unorthodox methods with some of her own. After getting bamboozled by Pironkova’s hard-to-read serve, Williams was twice forced to return with her non-dominant left hand, and twice won the point.