Serena Williams reacts after losing a point to Roberta Vinci, of Italy, during a semifinal match at the U.S. Open tennis tournament, Friday, Sept. 11, 2015, in New York. (AP Photo/Bill Kostroun)

NEW YORK – Shock waves rippled through Arthur Ashe Stadium on Friday afternoon.

Playing a semifinal match that was originally scheduled for Thursday night, but delayed by rain, Serena Williams’s superb summer came to a stunning end, two wins shy of completing the first calendar Grand Slam since 1988. Surprise semifinalist Roberta Vinci prevailed, 2-6, 6-4, 6-4.

Vinci came into the match as a serious underdog. The 32-year-old Italian had not played a top-10 seed in the fortnight, and had never beaten Williams – or even taken a set – in four previous meetings. A doubles specialist, this was her first grand slam singles semifinal. Even she hadn't thought she had a shot to beat the world's No. 1, she admitted to the crowd after the match.

“This is an incredible moment for me. It’s like a dream. I’m in the final. I beat Serena," she said on court after the win.

Vinci's initial expectations seemed to be accurate as Williams dominated the first set. Vinci earned an early break to lead 2-1, but Williams took the break right back, then smashed a huge winner to force break point at 3-2. She quickly converted, then converted again at 5-2 to take the set.

Williams faltered slightly to open the second set, double faulting to let Vinci build a 0-40 advantage, but battled all the way back to hold serve. It looked like she was in control. And the fans were completely in her corner.

Williams had said earlier in the week that she isn’t accustomed to being the fan favorite in New York, that the crowd usually likes to cheer on the underdog. But on Friday, everyone wanted to see a piece of history. They gasped when Vinci broke her to go up in the second set, then sounded pained when Vinci, against all odds, forced a third set. Vinci celebrated that set as though she’d won the match.

It was the second match in a row that Williams took the first set and dropped the second. It was the 12th time this year that she’s had to play a third set. But it’s nearly impossible to maintain momentum against Williams. She held serve to open the final set, then broke with a massive forehand slam to go up 2-0. She was four games from moving on.

But Vinci refused to cave, fighting back from 40-30 to break Williams in the third game. A huge break, followed by a quick hold to even the set at 2-all. Williams looked flat as she failed to take a point off Vinci’s serve. Was she starting to let the weight of the moment get to her? She was four games from advancing to the final, where she'd have attempted to tie Steffi Graf (the last player to complete the Grand Slam) with most major wins in the Open Era (22) and to pass Chris Evert with most U.S. Open wins (both have six).

Vinci took the first point off Williams’ serve in the next game. The crowd went ballistic when Williams evened it at 15-15, then went to 30-15. She crouched and screamed throughout that game, bellowing as she got to 40-15. Here was the ferocious fighter everyone had come to see. She held.

In her next service game, Williams built a 40-30 lead, but an error at the net kept the game going. She answered her own mistake with a 126mph ace to regain the advantage. The next point produced the best rally this tournament has seen. Williams nearly landed in the photographer’s pit as she attempted to reach the final shot. Back to deuce, then Vinci took the advantage, then held. The Italian was playing superb tennis. She led 4-3.

View photos Roberta Vinci celebrates after defeating Serena Williams. (REUTERS) More

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