Unseeded Roberta Vinci managed to dash Serena Williams’ quest for the Calendar Grand Slam by beating the tennis great 2-6, 6-4, 6-4.

The upset was huge, not just considering the year that Serena has enjoyed, but also because of Williams’ record against unseeded players in the U.S. Open.

Williams was attempting to become the first woman to complete a single season Slam since Steffi Graf accomplished the feat in 1988.

Vinci will face Flavia Pennetta in the final.

Needless to say, many on Twitter were stunned by the result even as many congratulated Serena on what has been an amazing year for her.

[ESPN]