Serena Williams on shock US Open loss to Roberta Vinci

Serena Williams refuses to talk about the disappointment of her shock defeat to Roberta Vinci in the US Open semi-finals.

Williams, 33, was two wins from completing the calendar Grand Slam but lost 2-6 6-4 6-4 to the unseeded Italian.

Former US Open champion Tracy Austin described it as "one of the biggest upsets in the history of tennis".

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