Serena Williams vs. Roberta Vinci: Score and Reaction from 2015 US Open

Roberta Vinci stormed back to shock Serena Williams with a three-set victory (2-6, 6-4, 6-4) to reach the finals of the 2015 U.S. Open on Friday. The loss—one of the most stunning in major tennis history—ends Williams' pursuit of the first calendar Grand Slam since 1988.

The match was originally scheduled for Thursday night before getting moved to Friday due to weather concerns. That didn't seem to have a significant impact on the play of either player, however. The bigger question will be how Vinci recovers for the final.

Williams commented before the match that getting to play the veteran Italian in Toronto last month helped her prepare, but she knew it would still be a difficult battle, as noted by Tom Sweetman of CNN.

"I'm not going to underestimate her," Williams said. "She has played really well. She's not in the semifinals of a Grand Slam for no reason. She knows what to do and she knows what to play. I just think it was great that I just played her because I kind of know what to expect, and I'll be more ready for it this time."

The top-ranked player in the world played some sloppy tennis at the outset. Some uncharacteristic errors basically handed the underdog a quick break. Richard Deitsch of Sports Illustrated tried to explain how big the upset would be:

Williams swiftly worked through the issues and broke right back in the very next game. In fact, she won five straight games from that point forward to get back level, take control and close out the opening set at 6-2.

Vinci simply didn't showcase enough weapons to seriously challenge the top seed after the opening few games. Once Williams stopped giving away free points, the set almost immediately turned into a runaway.

She particularly took advantage of the first-time major semifinalist's serve, as Christopher Clarey of the New York Times joked:

Vinci started to elevate her level of play in the second set. She began getting more first serves in to partially negate Williams' return and got better placement on her own return shots to force the top seed to move around the court.

It eventually allowed her to earn her second break of the match to take the lead in the set. The only difference this time was Williams could never get it back as her suddenly lackluster movement led to a stretch of mistake-laden tennis.

Vinci took advantage and managed to serve out the set to force a deciding third. The tactics weren't always conventional, but they were effective, as Bomani Jones of ESPN explained:

The tension also started to become more obvious for the American, per Tennis.com:

The roller coaster of emotions continued deep into the third set. After the two players traded breaks early, Vinci pushed herself out in front with a hard-fought break in the seventh game to grab a 4-3 edge. She proceeded to survive two break chances to consolidate it.

In the end, the third-set magic Williams enjoyed throughout the year finally came to an end Friday. Vinci only left a couple of openings, and the favorite could never capitalize, despite the feeling she was going to eventually take control again.

ESPN Stats & Info further illustrated the shocking nature of the result:

U.S. Open Tennis highlighted the final point of the upset:

Afterward, Vinci even apologized for winning, as Ben Rothenberg of the New York Times pointed out:

For her part, according to the U.S. Open's Twitter feed, Williams said, "I never felt pressure. I never felt pressure playing this tournament."

Williams was effusive in her praise for Vinci, saying, "She played literally out of her mind."

While there's no doubt Vinci played better over the last two sets, the No. 1 seed simply lost her rhythm and couldn't get it back in time to save the match.

It's a gigantic missed opportunity in terms of the calendar Grand Slam. As good as Williams has been throughout her career—and she should continue to serve as a top contender at majors moving forward—this was probably her best chance to accomplish the feat. She let it slip away.

Vinci moves on to face Flavia Pennetta in a championship match that suddenly carries far less intrigue. That's no disrespect to the finalists, who both earned their place, but there would have been a lot more interest in Williams trying to win the Grand Slam on home soil.

Pennetta holds a slight 5-4 edge in nine career meetings. The last matchup came in the U.S. Open quarterfinals two years ago, a routine triumph in straight sets for Pennetta. She should be the favorite once again despite Vinci's memorable semifinal win.