The Quest Is Over: Serena Williams Upset By Roberta Vinci In U.S. Open Semifinal

Serena Williams reacts after losing a point to unseeded Italian Roberta Vinci during a semifinal match at the U.S. Open tennis tournament on Friday. Williams went on to lose the match in three sets.

David Goldman/AP

Updated at 5 p.m. ET

The World No. 1 Serena Williams was upset by the unseeded Roberta Vinci of Italy 2-6, 6-4, 6-4, ending Williams' quest to win the first calendar Grand Slam since 1988.

Favored at 300-1 odds and having never lost a match to the 32-year-old Vinci, Williams seemed destined to move on to the U.S. Open final. When she won the first set 6-2 with relative ease, it looked all but guaranteed that she would find herself in the championship match.

But the Italian, who even admitted that she did not believe that she had a chance to win, played, as Williams said in her post-match interview, "out of her mind" to win the second and third sets.

Williams overcame her sister, Venus, in what was the most-watched tennis match of all time to set up the semifinal match against Vinci, and though talk of mounting pressure swirled around Williams all tournament, she denied that nerves had anything to do with the outcome.

"No I didn't feel pressure. I never feel pressure. I said that from the beginning," Williams said in the post-match interview. "I think [Vinci] played literally out of her mind."

Vinci did indeed play the match of her life, reaching the first major final of her career. NPR's Tom Goldman reported from the U.S. Open:

"Serena Williams committed 40 unforced errors to Vinci's 20 but a lot of Serena errors were because of Vinci. Vinci hit the ball beautifully today, her ground strokes, side to side, running Serena all over the court. Drop shots, lobs, she had Serena off balance for much of the time the last two sets."

In response to questions about how she felt about the loss, Williams said, "I don't want to talk about how disappointing it is for me. If you have any other questions, I'm open for that."

She also said, "I did win three grand slams this year. So yeah, I won four in a row. It's pretty good. It's definitely a positive."

For her part, Vinci credited her victory to being able not to "think about that [it was] Serena on the other court."

Vinci, aware that the New York audience was eager to witness history in the making, told the crowd, "Sorry guys. Sorry, but for me it's an amazing moment. It's incredible. ... It's the best moment of my life."

Here's how the tournament's website describes Vinci's path to the semifinal against Williams:

"Vinci, a 32-year-old tour vet, has advanced to this point through a combination of great play and bad luck. What figured to be her toughest test — a fourth-round face-off with the No. 25 seed Eugenie Bouchard — resulted in a walkover for the Italian after Bouchard was forced to withdraw with a concussion. But take nothing away from the gritty Vinci, who has toughed out three three-set wins in reaching her best major showing. Best known as one of the women's game's premier doubles talents, Vinci owns five career Slam doubles crowns, and she has achieved a career Grand Slam playing in pairs."

Vinci will face fellow Italian, 26^th seeded Flavia Pennetta in the first all Italian final in any major for men or women. Pennetta beat the No. 2 seed Simona Halep 6-1, 6-3 to secure her place in the final.

All smiles, Vinci said, "This is an incredible moment for me. It's amazing, like a dream. I'm in the final, I beat Serena, I'm—phewwww...." earning loud cheers from the assembled fans.

Vinci's emotional post-match interview charmed the crowd and you can watch it in it's entirety here.

The final will be Saturday at 3 p.m. ET on ESPN.