Djokovic takes heed of Nadal's injury woes
Updated: 2013-01-14 05:52
Novak Djokovic of Serbia and Serena Williams of the US dance Gangnam Style during the Kids Tennis Day on Saturday. Toby Melville / Reuters
World No 1 Novak Djokovic warned Rafael Nadal's injury woes showed the Grand Slam stranglehold exerted by the top men's tennis players was not unbreakable.