On the cusp of history, Serena Williams couldn't write the final chapter Friday.
With a calendar year Grand Slam on the line, Williams shockingly was beaten in the U.S. Open semifinals by unseeded Roberta Vinci, 2-6, 6-4, 6-4. Vinci not only had never beaten Williams in four previous matches, she had never won a set from her or taken more than four games in one.
But the 32-year-old Italian used her considerable guile to upset the No. 1 player in the world in a result that no one could have foretold, just as it couldn't be predicted that she would be facing Flavia Pennetta, her 33-year-old countrywoman, in Saturday's final.
Pennetta beat the No. 2 player in the world, Simona Halep, with surprising ease, 6-1, 6-3. The Arthur Ashe Stadium crowd was stunned.
Shortly after the match, Williams credited Vinci for the quality of her play and dismissed the question of disappointment for not adding the Open title to her 2015 Grand Slam portfolio of the Australian Open, French Open and Wimbledon.
"I don't want to talk about how disappointing it is for me," Williams said. "If you have any other questions, I'm open for that."
Williams rallied to take the first set after being broken in the third game. She changed rackets and used the new hammer to pound Vinci, particularly the Italian's second serve, which wasn't fast enough to get a speeding ticket on the Long Island Expressway.
Then Vinci craftily worked her way into the match. She started to serve better, moving Williams from side to side and from backcourt to the service box, where she seemed uncomfortable. It was a virtuoso performance from a player who never before had been in a Grand Slam semifinal.
"I thought she played the best tennis of her career. She's 33 [actually 32], she's going for it at a late age," said Williams, who turns 34 this month. "So that's good for her to keep going for it and playing so well. Actually, I guess it's inspiring. But yeah, I think she literally played out of her mind."
Though Williams served 16 aces and only four double faults, her thunderous clout didn't seem to faze Vinci, who picked up her timing on the serve as the match progressed.
"It's amazing. It's like a dream," Vinci said. "I'm really happy, but of course I'm a little bit really sad for Serena because she's incredible player, No. 1."
Toward the end of the deciding set, Vinci had to harness her emotions. "When I made the break [for 4-3] and serve, I was a little bit scared," she said. "My arms were like . I'm not joking . . . Stay calm, relax, breathe every single point. Don't think you have Serena on the other side of the court."
For her part, Williams said she was satisfied with the way she played.
"I don't think I played that bad," she said. "I made more unforced errors than I normally would make , but I think she played really well. She did not want to lose today. Neither did I, incidentally."
Gone for this season is Williams' chance to tie Steffi Graf with 22 total major titles, two behind Margaret Court's record of 24. Williams also had a chance to become the third woman, and first since Graf in 1988, to win the calendar year Grand Slam.
She did secure the "Serena Slam" when she won Wimbledon in July, having won four Slams in a row starting with the Open last year.
She deflected any thoughts that the pressure of the situation was too much for her.
"I told you guys I don't feel pressure," she said. "I never felt that pressure to win here. I said that from the beginning."
Now she has to be content with the Serena Slam.
"Like I said, I felt very happy to get that win at Wimbledon," Williams said. "I did win three Grand Slams this year. I won four in a row. It's pretty good. Yeah, so it's definitely a positive. Thank you."
With that she got up and left, with every intention of starting her Grand Slam crusade again in January.