SERENA WILLIAMS OUT OF US OPEN, AS SHE LOST TO ROBERTO VINCI.

 
Well, it's official: Serena Williams, the number one tennis player in the world and the sport's most dominant player for nigh on 15 years now, will not win the US Open. In a stunning upset, Serena Williams was bounced from the U.S. Open on Friday and lost her bid for the first Grand Slam in tennis in 27 years.

Her loss in Friday's semifinal against Italian player Roberta Vinci (2-6, 6-4, 6-4) was stunning — almost literally, for the 20,000 people in Arthur Ashe Stadium and the millions watching at home and online. Yes, upsets happen, but Williams not making the US Open was hardly even considered as a possibility. 2015 even marks the first year that the women's finals sold out before the men's. Everyone was waiting to see not if Williams would win, but how.

Here's why this loss will go down as one of the most stunning upsets in sports history.
While there are smaller matchups throughout the year, the four major tournaments in tennis are the Australian Open, the French Open, Wimbledon, and the US Open (in that order). Overall wins are counted as "Grand Slam" titles. These tournaments are played on different court surfaces: The French Open has clay courts, Wimbledon has grass, and the Australian and US Opens are both played on hard courts. As such, players who can compete at high levels on all three surfaces are both rare and prized.

It could be said that Williams favors hard courts, but her dominance proves she could wipe the floor with just about anyone, on any surface. Sure, there have been some dips and injuries along the way, but for the most part, Williams has been an unstoppable force.

The numbers are astonishing. Her career has spanned 16 years, from her first Grand Slam win in 1999 at age 19 to her win at Wimbledon earlier this year, at age 33. Out of the 25 major finals she reached, she has won 21: six each at Wimbledon, the US Open, and the Australian, and three at the French. By contrast, the leader in men's tennis is Roger Federer, who has won 17.

There are eight other active women's players who have won majors — and it takes all eight of them combined to match Williams's 21 titles.

To put it mildly: The odds of beating Serena Williams at her own game are not great.

Williams's command of the game has been so total that her winning has become noteworthy just because it's felt so inevitable. You could feel her opponents steeling themselves as they walked onto the court opposite her. Beating Serena Williams — even just for a set, if not the match — is a particular point of pride.

This holds especially true for Vinci, the woman who just knocked Williams out of the US Open. In her post-match interview, Vinci was visibly shocked, and often at a loss for words. Eventually, she came out with it: "I didn't expect that I [would win]."