Roberta Vinci pulled off one of the biggest upsets in tennis history when she defeated Serena Williams in the 2015 U.S. Open semifinals. Serena had won all three majors that season and, going for the calendar-year Slam, she was the heavy favorite over the unseeded Vinci. Serena took the first set, as expected, but Vinci took the next two for a 2-6, 6-4, 6-4 victory. She would subsequently lose to Flavia Pennetta, however, in her first Grand Slam singles final. Prior to reaching the final, the Italian had never before been past the quarterfinals at a major. Vinci has had the majority of her success as a doubles player. She completed the career doubles Grand Slam at Wimbledon in 2014, and ascended to No. 1 in the world in October of 2012. She owns a career 23-6 Fed Cup record, and was on Italy’s championship teams in 2006, 2009, 2010 and 2013.
Vinci's 2-6, 6-4, 6-4 victory over Serena Williams in the 2015 U.S. Open semifinals is one of the biggest upsets in tennis history: