Novak Djokovic delivered a lesson in Grand Slam tenacity to Learner Tien in the first round of the U.S. Open on Sunday as he battled past the American teenager 6-1 7-6(3) 6-2 and launched his latest quest for a record 25th major title.

Novak Djokovic thinks he came up with a way to get Serena Williams back on the tennis tour: Dare her to do it. A night after Williams stunned the tennis world by showing up to help induct rival Maria Sharapova into the International Tennis Hall of Fame,

Serena Williams has been urged by Novak Djokovic to return to the tennis circuit after the 23-time Grand Slam champion made a surprise appearance at the US Open