Djokovic, 38, beat Tien, 6-1, 7-6, 6-2 to improve to 19-0 in US Open first-round matches, tying Roger Federer for first all-time. But he labored with low energy, a nasty blister on his right big toe and Tien’s level, especially in the second set.

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,