MELBOURNE, AUSTRALIA - JANUARY 08: Serena Williams of the USA looks on during the launch of her Nike Training Club app workout on January 8, 2013 in Melbourne, Australia. (Photo by Scott ... more 

MELBOURNE, AUSTRALIA - JANUARY 08: Serena Williams of the USA looks on during the launch of her Nike Training Club app workout on January 8, 2013 in Melbourne, Australia. (Photo by Scott Barbour/Getty Images) less