Serena Williams retained her WTA Championships title on Sunday, coming from behind for a 2-6 6-3 6-0 win over China’s Li Na in Turkey.

It is the world No.1’s 78th win in 82 matches this year and her 11th title of 2013.

“I can’t believe I won – I was so tired.

“Did I really win? It’s really awesome – it’s such a special moment,” said the 32-year-old.

Williams becomes the first player to defend the title since Justine Henin in 2007.

The American won her fourth WTA Championship, having captured the elite tournament of the eight top-ranked players also in her debut in 2001 and in 2009 and 2012.

Williams will finish the year as the top-ranked player for the third time in her career after 2002 and 2009.

Li was in her first WTA Championship final and will finish the year at a career-high No.3.