Serena Williams crashes out of US Open in one of the most stunning upsets in tennis history

Serena Williams' hopes for a calendar grand slam were dashed as she was eliminated from the US Open by 43rd-ranked Italian player Roberta Vinci.

Serena, the world No. 1 and the heavy favorite to win the US Open, looked like she would cruise to an easy win after winning the first set 6-2.

But in the second set, Vinci stormed back to win 6-4, setting up a dramatic third set. Though Serena was up 2-0, Vinci once again stormed back, breaking Serena to go up 4-3 and then winning the next game.

Serena moved the score closer to make it 5-4, but lost the following game and the match as Vinci served.

Serena seemed fatigued by the third set, perhaps because she's hardly ever pushed to such lengths. According to ESPN, Williams' unforced errors kept growing by the set:

The 32-year-old Vinci seemed elated after the match, saying, "It's an incredible moment for me. It's like a dream."

Williams was classy in the defeat, noting how well Vinci played:

The final is set up for Vinci to take on a fellow Italian, 26th-ranked Flavia Pennetta.