Gutsy Venus Williams has saved five match points, before her 21st US Open campaign was ended by Elina Svitolina.
Serving to stay in the match, the 39-year-old American showed her never-say-die spirit remains undimmed in a marathon penultimate game.
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She forced Svitolina to serve for the match, but the Ukrainian fifth seed eventually crossed the line for a 6-4 6-4 victory on Wednesday.
"It was a really incredible match," Svitolina said. "It was really special.
"It's unbelievable what Venus does, on and off the court - she is a big inspiration.
"I had to stay very focused and try to put an extra ball over the net. She knows how to handle moments like this.
"It was incredibly tough and only a few points decided the match."
Third-seed Czech Karolina Pliskova, 27, is also through to the third round, beating Georgia's Mariam Bolkvadze 6-1 6-4.
Also advancing is Madison Keys, who eased through, after a slow start and an early loss of serve to beat China's Zhu Lin 6-4 6-1.
Tenth-seeded Keys, who lost in the 2017 US Open final to fellow American Sloane Stephens, struck 31 winners in front of an enthusiastic home crowd.
Zhu, who exited the first three Grand Slams of the year in the first round, converted two of three break-point opportunities, but struggled to cause problems for her opponent.
"I think she came out and she was playing really well," Keys said of Zhu. "I just kind of stuck to my game and knew that I'd have an opportunity, and stayed calm."
PA
