WHAT HAPPENED: In one of the most shocking upsets in US Open history, if not sports history as a whole, unseeded and unheralded Italian Roberta Vinci – at 32 the oldest first-time Grand Slam semifinalist in the Open era – stopped world No. 1 Serena Williams’ quest for the calendar-year Grand Slam with an against-all-odds, 2-6, 6-4, 6-4 triumph.

In addition to her Grand Slam attempt, Williams was aiming to equal Steffi Graf’s all-time mark of 22 career majors and break a tie with Chris Evert for the most US Open singles titles in the Open era. But it was not to be.

“It’s an incredible moment for me. It’s amazing. Its like a dream,” said Vinci, a 300-1 underdog, with tears in her eyes. “I’m in the final and I beat Serena. Sorry, guys. But for me it’s an amazing moment. I tried to stay focused and not think about the match. Serena’s an incredible player. I think it’s the best moment of my life.”

She then underlined her apology to the pro-Serena crowd, saying, “Today is my day. Sorry, guys.”

“I thought she played the best tennis of her career,” Williams said in her post-match press conference. “I think she played literally out of her mind.”

Vinci, 32, will meet countrywoman Flavia Pennetta in an all-Italian final, the first time two Italian women will meet in a Grand Slam final in the Open era. Pennetta holds a 5-4 edge in nine previous encounters, their most recent a quarterfinal clash here in 2013, won by Pennetta, 6-4, 6-1.

Williams opened the first set authoritatively with a 92 mph ace, but it was her diminutive 5-foot-4 Italian foe who would score the first break of the match, when an errant forehand floated long at 1-all. However, it didn’t take long for the world No. 1 to find the kind of championship form that had carried her to 33 consecutive Grand Slam-level victories. The 33-year-old American would grab the next three breaks to take the set in a mere 31 minutes.

Vinci, who until the semis hadn’t played a single point against a seeded player, benefitting from the round-of-16 withdrawal of No. 25 Eugenie Bouchard, was her usual crafty self. Vinci employed a throwback, old-school arsenal of one-handed slice backhands and well-timed drop shots, and soon worked her way back into the match. Serving for the second set at 5-4, she fought off a break point to pull even at a set apiece. Williams would take out her frustration on her racquet, earning a warning from the chair umpire.

The outburst seemed to spur Williams, briefly easing the tense atmosphere in Arthur Ashe Stadium, whose seat-holders were beginning to wonder if they might be in for an upset for the ages. She went up a break at 2-0 in the final set. But with Serena serving and the stanza back on serve at 3-3, Vinci capped a grueling ground exchange with a backhand volley winner and raised her arms to the Flushing sky in an attempt to win over at least some of the partisan crowd, as if saying, “SHOW ME SOME LOVE, TOO!” She would go on to earn the break and a 4-3 advantage.

Two games later, at 2:56 p.m. Eastern Standard Time, she stepped up to serve out the match at love, appropriately capping her unforeseen comeback with a forehand volley winner. She bent over in disbelief as Serena walked off the court, having suffered what has to be considered the most devastating defeat of her storied career.   

Williams totaled 16 aces in the two-hour final-four clash, finishing with a US Open-best 54 over six matches. But despite a 50 to 19 advantage in winners over her opponent, it wasn’t enough on Day 12 at the US Open.

WHAT IT MEANS: The Italian duo of Vinci and Pennetta became only the third and fourth Italian women to reach a Grand Slam final after Francesca Schiavone, who reached back-to-back finals at Roland Garros in 2010, and Sara Errani, who reached the Roland Garros final in 2012.

QUESTION: At 33, will Serena Williams ever put herself in position to win a calendar-year Grand Slam again?

September 11, 2015 - Roberta Vinci celebrates her win over Serena Williams in a women's singles semifinal match during the 2015 US Open at the USTA Billie Jean King National Tennis Center in Flushing, NY. (USTA/Pete Staples)