<P> Williams played one match at the Swedish Open in Båstad before withdrawing with an elbow injury . She was the defending champion at the Bank of the West Classic but withdrew from the tournament in order for her elbow to get better . Williams had her 19 match winning streak ended by 18 - year - old Swiss Belinda Bencic, the No. 20, in three tight sets in the semifinals of the Canadian Open . It was her second defeat of the year and first on hard courts since the 2014 WTA Finals . The next week Williams defended her title at the Western & Southern Open with a straight sets victory over No. 3 Simona Halep for her 69th WTA title, breaking a tie with Evonne Goolagong for standalone fifth-most WTA titles won . Williams's attempt at capturing the "Grand Slam" (winning all four Grand Slams in a calendar year) came to an end in the semifinals of the US Open, where she lost to Roberta Vinci in three sets . The loss has been described by some as one of the biggest upsets in tennis history . Nonetheless, Williams secured the year - end No. 1 ranking with her results at the tournament . On October 1, Williams called an end to her season, stating that she had been injured for most of the year and wanted to address her fitness issues . Prior to the announcement, coach Patrick Mouratoglou hinted that Williams might not play again in 2015 due to a lack of motivation and disappointment following her loss at the Open . On October 5, Williams surpassed Chris Evert for third-most weeks ranked world No. 1 . Williams held the No. 1 ranking the entire season for the second consecutive year, finishing there for the fifth time in her career . She was voted WTA Player of the Year for the seventh time in her career . On December 14, Sports Illustrated announced Williams as their Sportsperson of the Year . She thus became the third solo woman, and first since 1983, to receive the award . Williams was also named ITF World Champion for the sixth time in her career . Soon after, it was announced that she was voted Female Athlete of the Year by the Associated Press for the fourth time . </P> <Table> <Tr> <Td> </Td> <Td> This section of a biography of a living person needs additional citations for verification . Please help by adding reliable sources . Contentious material about living persons that is unsourced or poorly sourced must be removed immediately, especially if potentially libelous or harmful . (July 2016) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section of a biography of a living person needs additional citations for verification . Please help by adding reliable sources . Contentious material about living persons that is unsourced or poorly sourced must be removed immediately, especially if potentially libelous or harmful . (July 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> Williams withdrew from the Hopman Cup after retiring from her singles match against Australia Gold with inflammation of her left knee . Her next tournament was the Australian Open, where she was the No. 1 seed and defending champion . She reached the final without dropping a set, including wins over No. 5, Maria Sharapova, and No. 4, Agnieszka Radwańska, and faced first time Grand Slam finalist Angelique Kerber . She was considered the heavy favorite to win the title, as she had never lost an Australian Open final or semifinal . She also dominated the head - to - head against Kerber, having lost only once in six meetings and having not lost a set to her in four years . However, Williams lost the final in three sets and Kerber won her first Grand Slam title . This marked Williams's first - ever loss in the final of the Australian Open, as well as her first three - set loss in the final of a Grand Slam . She had previously been 6--0 and 8--0 respectively . </P>

How old was serena when she won her first major title