It has got to be one of the biggest upsets in tennis history - unseeded Roberta Vinci knocked off #1 Serena Williams 2-6 6-4 6-4 in the semi-final round at the U.S. Open.

There will be no calendar grand slam for Williams. She was attempting to win all majors in the same year for the first time since Steffi Graf  did it in 1988.

Vinci will now play Flavia Pennetta in Saturday's championship match. Pennatta knocked off #2 seed Simona Halep.