New York: Unheralded Italian Roberta Vinci pulled off one of the biggest upsets in tennis history here on Friday, rallying to defeat Serena Williams 2-6, 6-4, 6-4 in the US Open semifinals.

The 43rd-ranked Vinci, who is best known for her achievements in doubles and had never won a set in four previous matches against the 21-time Grand Slam champion, will next take on 26th-seeded countrywoman Flavia Pennetta in tennis- first-ever all-Italian major singles final.